Review of the Deep-Sea Genus Argyropeza (Gastropoda: Prosobranchia: Cerithiidae) RICHARD S. HOUBRICK SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY ? NUMBER 321 SERIES PUBLICATIONS OF THE SMITHSONIAN INSTITUTION Emphasis upon publication as a means of "diffusing knowledge" was expressed by the first Secretary of the Smithsonian. In his formal plan for the Institution, Joseph Henry outlined a program that included the following statement: "It is proposed to publish a series of reports, giving an account of the new discoveries in science, and of the changes made from year to year in all branches of knowledge." This theme of basic research has been adhered to through the years by thousands of titles issued in series publications under the Smithsonian imprint, commencing with Smithsonian Contributions to Knowledge in 1848 and continuing with the following active series: Smithsonian Contributions to Anthropo/ogy Smithsonian Contributions to Astrophysics Smithsonian Contributions to Botany Smithsonian Contributions to the Earth Sciences Smithsonian Contributions to Paleobiology Smithsonian Contributions to Zoology Smithsonian Studies in Air and Space Smithsonian Studies in History and Technology In these series, the Institution publishes small papers and full-scale monographs that report the research and collections of its various museums and bureaux or of professional colleagues in the world cf science and scholarship. The publications are distributed by mailing lists to libraries, universities, and similar institutions throughout the world. Papers or monographs submitted for series publication are received by the Smithsonian Institution Press, subject to its own review for format and style, only through departments of the various Smithsonian museums or bureaux, where the manuscripts are given substantive review. Press requirements for manuscript and art preparation are outlined on the inside back cover. S. Dillon Ripley Secretary Smithsonian Institution SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY ? NUMBER 321 Review of the Deep-Sea Genus Argyropeza (Gastropoda: Prosobranchia: Gerithiidae) Richard S. Houbrick SMITHSONIAN INSTITUTION PRESS City of Washington 1980 A B S T R A C T Houbrick, Richard S. Review of the Deep-Sea Genus Argyropeza (Gastropoda: Prosobranchia: Cerithiidae). Smithsonian Contributions to Zoology, number 321, 30 pages, 12 figures, 8 tables, 1980.?An historical review of the genus Argyropeza is presented. The assignment of the genus within the Cerithiidae is clarified. A close relationship between Argyropeza and Bittium is suggested. Argyropeza species live on soft sediments of continental slopes and island groups in the Indo-Pacific and occur most frequently at bathyal depths. They have pelagic larvae and are sediment feeders. Five nominal species are recognized: Argyropeza divina, A. izekiana, A. schepmaniana, A. verecunda, and A. leucocephala. An appendix with species frequently assigned to or easily confused with Argyropeza is included. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: The coral Montastrea cavernosa (Linnaeus). Library of Congress Cataloging in Publication Data Houbrick, Richard S Review of the deep-sea genus Argyropeza (Gastropoda, Prosobranchia, Cerithiidae) (Smithsonian contributions to zoology ; no. 321) Bibliography: p. Includes index. 1. Argyropeza?Classification. 2. Mollusks?Classification. I. Title. II. Series: Smithsonian Institution. Smithsonian contributions to zoology ; no. 321. QL1.S54 no. 321 [QL430.5.C4] 591s [594'.32] 80-607017 Contents Page Introduction 1 Abbreviations 1 Acknowledgments 1 Historical Review 2 Superfamily CERITHIACEA Fleming, 1822 2 Family CERITHIIDAE Fleming, 1822 2 Subfamily CERITHIINAE Fleming, 1822 2 Genus Argyropeza Melvill and Standen, 1901 2 Argyropeza divina Melvill and Standen 6 Argyropeza izekiana Kuroda 12 Argyropeza schepmaniana Melvill 17 Argyropeza leucocephala (Watson) 20 Argyropeza verecunda (Melvill and Standen) 22 Appendix 26 Literature Cited 28 ni Review of the Deep-Sea Genus Argyropeza (Gastropoda: Prosobranchia: Cerithiidae) Richard S. Houbrick Introduction The genus Argyropeza comprises five bathyal species of small, vitreous-shelled cerithids and is not well known. The systematic position of the genus within the Cerithiacea has been uncertain since Argyropeza was first proposed and described by Melvill and Standen (1901:372). The taxon- omy of Argyropeza species has also been poorly understood due to the scattered literature, lack of specimens, and inadequate analysis of shell char- acters. Virtually nothing has been written about radulae, opercula, or internal anatomy and no attention has been given to the ecology and zo- ogeography of the genus. Numerous specimens of Argyropeza species were dredged by the U.S. Fisheries steamer Albatross in the western Pacific (1907-1910) and were depos- ited in the National Museum of Natural History. Ecological and bathymetric data were provided with each lot. I examined these specimens and additional material from other museums that provided adequate material for statistical analysis of each species. All measurements were made on adult specimens. The number of whorls on each shell were counted after the sharp transition be- Richard S. Houbrick, Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC. 20560. tween protoconch and teleoconch. No preserved animals were available for dissection or section- ing. Several shells of a few species contained dried animals from which radulae and opercula were extracted and some anatomical features were studied. In this revision I have used scanning electron micrographs of radulae, protoconchs, shell sculpture, and opercula for character anal- ysis. ABBREVIATIONS.? AMS Australian Museum, Sydney ANSP Academy of Natural Sciences of Philadel- phia BM(NH) British Museum (Natural History) MNHN Museum National d'Histoire Naturelle, Paris NSMT National Science Museum, Tokyo SEM Scanning electron micrograph USNM former United States National Museum, collections in the National Museum of Natural History, Smithsonian Institution ACKNOWLEDGMENTS.? I wish to thank Drs. Jo- seph Rosewater and Harald Rehder, Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, for crit- ically reading a draft of this paper and for their assistance during its preparation. I am indebted to Dr. Winston Ponder of the Australian Mu- seum, Sydney, for the loan of specimens in his charge and for useful discussion about the rela- 1 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY tionships of some higher Cerithiacean taxa. I also thank him for critically reading an early draft of this paper. Dr. John Taylor, of the British Mu- seum (Natural History) kindly sent photographs of some of the types. Dr. Philippe Bouchet, of the Museum d'Histoire Naturelle, Paris, kindly al- lowed me to examine specimens in his charge. For assistance with the SEM and preparation of the photomicrographs I thank Ms. Susanne Bra- den, Scanning Electron Microscope Laboratory and Mr. Victor Krantz, Photographic Services, of the National Museum of Natural History, Smithsonian Institution. Technical assistance was kindly given by Miss Cathy Lamb and Miss Cindy Gust, Department of Invertebrate Zoology, National Museum of Natural History, Smithson- ian Institution. Historical Review Melvill and Standen (1901:372) were unsure about the taxonomic allocation of Argyropeza when they originally proposed it and provision- ally assigned it "as an outlying form of Cerithi- idae or Litiopidae." Schepman (1909:170) consid- ered the genus related to Cerithiopsis and Litiopa because of some similarities of the radulae but noted that the operculum of Argyropeza was dif- ferent. Although unsure of its relationships, he regarded Argyropeza to be a valid genus. Thiele (1918:120) observed that the radula and opercu- lum of Argyropeza were similar to those of Bittium and he later regarded it as a subgenus of Bittium (Thiele, 1931:212). Hornungand Mermod (1926: 207; 1928:115) referred Argyropeza to the Litiopi- dae and described two new species. Kuroda (1949:79) thought that A. izekiana was a deep sea representative of Bittium. Argyropeza was also as- signed next to Bittium by Shuto (1969:64). Noth- ing substantial has been written about Argyropeza until recently when it was reviewed by Griindel (1976), who considered the systematic position of the genus and assigned it to the Procerithiidae Cossmann, 1905. Superfamily CERITHIACEA Fleming, 1822 Family CERITHIIDAE Fleming, 1822 Subfamily CERITHIINAE Fleming, 1822 Genus Argyropeza Melvill and Standen, 1901 Argyropeza Melvill and Standen, 1901:371-372 [type-speeies, by monotypy, Argyropeza divina Melvill and Standen, 1901].?Schepman, 1909:169.?Hornung and Mermod, 1926:207.?Thiele, 1931:212.?Wenz, 1940:757.?Ku- roda, 1949:76.?MacNeil, 1960:40.?Franc, 1968:281.? Getting, 1974:130.?Griindel, 1976:40.?Ladd, 1977:15. Argyropeda [sic] Shuto, 1969:63-65. DESCRIPTION.?Shell small, 6-8 mm in length, thin and vitreous, turreted and with 9-12 whorls sculptured with weak axial riblets and with two spiral cords bearing sharp nodules where crossed by axial riblets. Sinusigera protoconch of about three and a half whorls, sculptured with two spiral lirae and spiral band of pustules adjacent to suture. Tip of protoconch smooth, dome- shaped, white, remainder chestnut in color. Pro- toconch sculpture sharply separated from adult sculpture of teleoconch. Former varices present on shell, with prominent varix opposite outer lip of aperture. Suture deeply impressed, set off with inferior and superior sutural ramps. Aperture ovate with short but distinct anterior siphonal canal and weak anal canal. Outer lip thin, colu- mella concave. Operculum thin, corneous, subcir- cular, and multispiral with subcentral nucleus. Animal has large snout and broad cephalic ten- tacles with large eyes at their bases. Mouth with triangular jaws and taenioglossate (2+1 + 1 + 1+2) radular ribbon. Radula with quadrate rachidian tooth and trapezoidal lateral tooth that is lat- erally elongate and is serrated with small denticles along its cutting edge. Marginal teeth long and slender and serrated, pointed tips. REMARKS.?The name Argyropeza is derived from the Greek feminine noun arguropeza ("silver foot"), the Homeric epithet of Thetis. The genus comprises five living shelf species, A. divina, A. NUMBER 321 izekiana, A. verecunda, A. schepmaniana, and A. leu- cocephala. They occur throughout the tropical shelf regions of the western Pacific, southeast Asia, and the Indian Ocean. The genus may be traced back to the Pliocene in the geological record. There have been a number of species erro- neously assigned to the genus Argyropeza. Two of these, Argyropeza melvilli Schepman, 1909, from the Sulu Sea, and Argyropeza suvaensis Ladd, 1977, from Fiji, should be referred to the genus Abysso- chrysos Tomlin, 1927, family Abyssochrysidae Tomlin, 1927. As Barnard (1963:144) noted, Schepman (1909:170) was doubtful about the generic assignment of A. melvilli Schepman, but at Melvill's suggestion, referred it to Argyropeza. The anatomy, shell, and radula of A. melvilli unequivocally confirm Barnard's (1963:144) transfer of Argyropeza melvilli to Abyssochrysos (Houbrick, 1979:12). Ladd (1977:15) described Argyropeza suvaensis, a fossil from early Miocene of Fiji, but only tenta- tively assigned it to the genus Argyropeza. He suggested that his fossil specimens were conspe- cific with Argyropeza melvilli Schepman, which I have shown is an Abyssochrysos species (Houbrick, 1979). Ladd (1977:15) noted that MacNeil (1960: 43) believed that Schepman's specimen was an Alipta Finlay, 1926, family Cerithiopsidae. This is clearly an erroneous assignment because the pro- toconch and radula of Alipta are very different from those of Argyropeza or Abyssochrysos (see Mar- shall, 1978:62-63, fig. 6, a-c). I have examined Ladd's type-material of Argyropeza suvaensis and believe that this species is probably conspecific with Abyssochrysos melvilli (Schepman). Argyropeza involuta, described by Thiele (1918: 120) from two immature specimens and frag- ments of a third without a complete outer lip, was erroneously assigned to the genus Argyropeza. Both the description and examination of the hol- otype convince me that this species is conspecific with Cerithium bicanaliferum Brazier, 1877, a species that is clearly unrelated to the Argyropeza group. The species described by Hornung and Mer- mod (1926:208) as Argyropeza doriae is not a mem- ber of this genus. The protoconch, shell sculpture and aperture do not fit the limits of Argyropeza. I regard Argyropeza as a valid genus for a num- ber of reasons. (1) The shells of the five species have distinct anterior siphonal canals and deeply impressed sutures that are set off by sloping in- ferior and superior sutural ramps. The shells are vitreous, sculptured similarly with weak axial riblets and spiral cords set with small, sharp nodules. All Argyropeza species have small shells that are vitreous, thin and bear several randomly placed varices, the most prominent one being opposite the outer lip of the aperture. (2) They share identical protoconchs suggesting that all have similar developmental modes and plank- tonic larvae. (3) Although the radulae of only two species are known, they are virtually identical and indicate a homologous feeding function; moreover, the fecal pellets of these species are also identical and composed of fine sediment. (4) The two species from which animals are known have similar external anatomical features. (5) All known species live in deep water environments and are found on the same kind of fine sand and mud substrata. PHYLETIC RELATIONSHIPS.?Argyropeza has been assigned by various workers to the families Dias- tomidae Deshayes, Litiopidae H. and A. Adams, Dialidae A. Adams, and Cerithiidae Fleming. The characters, limits, and taxonomic positions of the first three families are problematic because they have been proposed on shell characters alone. For instance, Diastoma Deshayes, 1850, of the Diastomidae, is based upon an Eocene species, Diastoma costellata (Lamarck), from the Paris Basin and comprises mostly fossil species. Ludbrook (1941) recently reviewed this group. The only living species, Diastoma melanoides (Reeve, 1849), is found in a restricted area in southwestern Aus- tralia and its anatomy and radula are unknown. The operculum is cerithioid. The shells of all Diastoma species are relatively large and have SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY smooth outer lips that lack anterior siphonal ca- nals. I thus exclude Argyropeza from this group. The Litiopidae, as exemplified by Litiopa, which lives on pelagic algae, bears little resem- blance to Argyropeza in shell characters, radula, or ecology. Moreover, Litiopa has opercular and epi- podial tentacles (pers. observ.) not seen in Argy- ropeza. I thus dismiss the family Litiopidae as a correct assignment for Argyropeza. The Dialidae are an unlikely family in which to place Argyropeza. Although Diala has been re- ferred to the Diastomidae and the Cerithiidae by various workers, Diala species lack an anterior canal, a feature always present in members of the Cerithiidae; moreover, they tend to have thin, squat shells, smooth protoconchs, flatter whorls, and a lower aperture-length to shell-length ratio than do Argyropeza species. They also lack former varices and axial ribs. Living Diala snails have epipodial tentacles, an antomical feature not pres- ent in the Cerithiidae. I thus consider this group totally unrelated to Argyropeza. The relationship of Argyropeza to other supra- specific taxonomic groups in the Cerithiidae is difficult to assess because many of the smaller shelled genera in the family are not sharply de- fined and are either artificial or parochial in scope. Moreover, there is little known about the anatomy, radulae, or biology of these taxa (see Houbrick, 1975; 1977). Although some anatomi- cal features of Argyropeza species are described in this paper, the detailed anatomy of the open pallial gonoducts remains unknown because the material I examined was too poorly preserved for critical study of internal ducts. It is thus impos- sible to make reliable anatomical comparisons with other groups. Argyropeza is frequently confused with the genus Fenella A. Adams, 1860 (= Obtortio Hedly, 1899; = Eufenella Kuroda and Habe, 1952), but true Fenella species all lack an anterior canal and should probably be considered members of the families Dialidae or Diastomidae. There is also some confusion about the status of the genus Alaba. Alaba species have epipodial tentacles and their shells lack an anterior canal; thus, they too should be assigned to the Dialidae or Diastomi- dae. There are a number of small cerithid-like snails lacking epipodial tentacles and with slight ante- rior canals that are frequently placed in the genus Fenella. These are probably members of the genus Alabina (W. F. Ponder, pers. comm., 1979). Al- though Alabina has been considered a synonym of Fenella, it is obviously better referred to the Ceri- thiidae and is probably close to Bittium. More anatomical information and radular studies are needed to assess the relationship of Alabina to Bittium and Argyropeza. Hornung and Mermod (1926:207) considered Argyropeza to be closely related to, or synonymous with, the genus Glosia Cossmann, 1921, which they placed in the family Litiopidae. Glosia species do not have an anterior siphonal canal and are here regarded as members of the Diastomidae. Hornung and Mermod also believed that Alabina Dall 1902 was a synonym of Argyropeza. As noted above, there is not enough data to justify this conclusion. Griindel (1976:40) noted a morphological sim- ilarity between Argyropeza and the Jurassic genus Cryptaulax (Xystrella), which he referred to the family Procerithiidae. He (1976:44) thus assigned Argyropeza to the family Procerithiidae Cossmann, 1906, subfamily Cryptaulinae Griindel, 1976, and placed Bittium in the same family, subfamily Pro- cerithiinae Cossmann, 1905. I find Griindel's (1976) revision of the "Bittium Group" unsatis- factory for a number of reasons. Although his classification is based on fossils and a few living species, his analysis employed shell characters alone and ignored biological data. Griindel (1976) placed undue emphasis on protoconch morphol- ogy in developing a phylogeny for this group. It has been shown that protoconchs differ according to the mode of larval development (direct or indirect) and that developmental modes fre- quently vary between species within the same genus and sometimes within a single species (see Robertson, 1976:227-232, for an excellant re- view). I have shown two kinds of development occur in Cerithium species (Houbrick, 1970; 1974a; NUMBER 321 1974b) and the same phenomenon has been cited for the Cerithiopisidae (Marshall, 1978). Thus, a classification of supraspecific taxa based upon protoconch morphology does not necessarily re- flect phylogeny and may be misleading. Griindel (1976:40) mistakenly interpreted the sinusigera notch of the protoconch as a varix, whereas it indicates a dramatic change in environment and the beginning of new growth and shell sculpture. It is thus not exactly the same as a typical growth varix. He also stated that the aperture of Argyro- peza lacked a clear canal. This is incorrect, as a cursory glance at the plates in this paper will show. As a result of (he undue emphasis on differences in shell sculpture, Griindel's (1976) classification is artificial and topheavy with su- praspecific taxa. I prefer to disregard the higher taxonomic categories used by Griindel (1976) and consider Argyropeza and Bittium to be closely re- lated genera in the family Cerithiidae. Griindel (1976:46) proposed a new genus, Var- icopeza, for a living species from the South China Sea that he named Varicopeza varicopeza. He be- lieved Varicopeza was closely related to Argyropeza and Cryptaulax. His plates indicate that the spec- imens he used had missing apertures. Griindel's species, Varicopeza varicopeza, is a synonym of Cer- ithium bicanaliferum Brazier, 1877 (also known as Cerithium trigonostomum Melvill, 1910). I have ex- amined numerous specimens and the embryonic whorls, radula, shell, distinctive aperture, and anal canal of Cerithium bicanaliferum are different from those of Argyropeza species. The evidence derived from analysis of adult shell physiognomies, protoconchs, radulae, and opercula indicates that Argyropeza should be re- ferred to the family Cerithiidae Fleming. Adult Argyropeza shells are much thinner and vitreous than those of Bittium but both genera are alike in having shells with distinct former varices present, the strongest one being opposite the outer lip of the aperture. Their general shell physiognomies are also similar but the suture of Argyropeza species is more deeply impressed. The larval shells or protoconchs of Argyropeza are distinctive due to a single spiral row of pustules adjacent to the suture but are otherwise similar to those of some Ceri- thium species or somewhat like those depicted for Bittium by Griindel (1976:41, figs. 9-12) and Richter and Thorson (1975:166, pis. 3-4). The protoconchs of species in both genera consist of about three and a half whorls and are sculptured with two spiral lirae that begin to appear on the third whorl. They also have a deep sinusigera notch. Some Bittium and Cerithium species have tiny pustules covering the third whorl of the protoconch. Thus, although Argyropeza proto- conchs are distinctive, they share some characters with those of Bittium and Cerithium. Both Bittium and Argyropeza species have similar radulae. The radula of Bittium differs in having marginal teeth with more spatulate tips and lat- eral teeth that have long vertical extensions on the lower plate of the tooth. The cutting edge of the lateral teeth is also serrated with fewer den- ticles than Argyropeza. The opercula of species in both genera are cerithioid, but there are more spirals in Argyropeza. Although these similarities may be due to con- vergence, they are the only lines of evidence now available for phyletic speculation and, taken in their totality, are probably reliable. I thus concur with the opinion of previous authors, as outlined above, that Argyropeza is probably closely related to the genus Bittium. Although Bittium is some- times placed in the subfamily Bittinae, I prefer not to recognize this subfamily or other higher categories proposed for the Bittium group because our present state of knowledge lends no biological or phyletic significance to them. My views on this subject have been discussed in more detail else- where (Houbrick, 1977). INTERSPECIFIC RELATIONSHIPS.?Due to the lack of anatomical characters, any remarks about in- terspecific phylogeny of the five Argyropeza species are of necessity largely speculative. The only con- sistent characters available for all species are those derived from the shell. I have used a multi-char- acter analysis to express phylogeny by seeking to determine the primitive or derived state of each character. Evidence from ontogeny, stratigraphic position, and outgroup comparison has been used SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY to determine the state of a character. Ontogeny assumes that a character state appearing first in development is more generalized than one ap- pearing later; in other words, ontogeny recapitu- lates phylogeny often enough that it can help to determine polarity. Stratigraphic position is a useful criterion because the earlier the first ap- pearance of a character, the more likely it is to be primitive. Outgroup comparison determines the occurrence of the characters in a related group. While I realize that this method is unsatisfac- tory in many respects, it utilizes the only available information about this deep-sea group. A clado- gram showing inferred relationships is presented below in Figure 1. The character states chosen for analysis are presented in Table 1. Of the five species, Argyropeza divina is unique in physiog- nomy, simple in shell sculpture, and attains the largest size. It has the widest geographic distri- bution and occurs in the greatest concentrations. This species has been recorded from the Pliocene to the Recent and is thus the oldest known Argy- TABLE 1.?Character states used in the construction of a phylogeny for Argyropeza species IZEKIANA SCHEPMANIANA LfUCOCEPHALA FIGURE 1.?Inferred phylogeny of Argyropeza species. character shell length shell width aperture length aperture length shell length number of whorls spiral cords axial riblets apical angle primitive high high high low high few few high derived low low low high low mny many low ropeza taxon. The shell characters of this species are thus assumed to be the most primitive of the group. It is interesting to note that all species begin growth with two spiral cords per whorl. Argyropeza izekiana shares with A. divina large size, a simple shell sculpture of two spiral cords, sharp nodules, and 12.5 axial riblets. Argyropeza schep- maniana is known as a fossil from the Pleistocene, has three spiral cords and 13.5 axial riblets and appears to be related to A. leucocephala. Both of these species share sculptural similarities with A. verecunda, the smallest and most elaborately sculp- tured species of the group. Table 2 presents a comparative list of shell characters. ECOLOGY.?All specimens of Argyropeza have been dredged from deep-sea shelves or slopes on muddy or fine grained substrata where they fre- quently occur in large populations. Table 3 shows the depth ranges of different species. All live in TABLE 2.?Comparison of Argyropeza species, using shell characters (measurements in mm; based on mean values) species divina izekiana schepmaniana leucocephala verecunda no. 20 20 20 10 5 length 6.96 4.63 4.14 3.88 2.77 width 2.21 1.53 1.28 1.20 0.98 aperture length 1.85 1.09 0.77 0.76 0.55 aper. length aper. width 3.80 4.27 5.40 5.10 5.04 no. whorls 9 8 8 7 8 no. spiral cords 2 2 3 3 4 no. ribs 12.5 12.5 13.5 16.5 14.5 apical angle 35? 35? 32? 22? 32? NUMBER 321 the bathyal zone as defined by Hedgpeth (1957: 18) where they appear to be confined to conti- nental slopes. The stomach contents and fecal pellets of A. divina and A. izekiana contain fine particles of sand, detritus, and a few foraminifer tests. This evidence and radular morphology indicate that Argyropeza species are probably detritivores that eat the sediments on which they live. Although the spawn of Argyropeza species is not known, the protoconchs of all species bear dis- tinctive sculpture and have a clear sinusigera notch, indicative of a planktotrophic larval phase. This may account for the wide, but sometimes spotty distribution of most species and indicates that genetic exchanges can occur between popu- lations, a fact well documented by Bouchet (1976) and Bouchet and Wafen (1979) for other deep- sea prosobranchs. TABLE 3.?Bathymetric species divina izekiana schepmaniana verecunda leucocephala distribution of Argyropeza species no. of stations d e P t h r a r ^ e t m e t e r s ' 75 70 44 3 1 58-923 49-914 33-914 39-285 133 mean depth 356 307 145 162 sd 196.04 159.83 176.00 123.00 Argyropeza divina Melvill and Standen FIGURES 2-4 Argyropeza divina Melvill and Standen, 1901:371-372, pi. 21: fig. 3 [holotype: BM(NH) Reg. No. 1887.2.9.1749, type- locality: 24?05'N, 57?35'E., Gulf of Oman, 375 m].? Schepman, 1909:169-170, pi. 21: fig. 3.?Melvill, 1912: 246-247, pi. 12: fig. 10.?Grundel, 1976:44, pi. 1: figs. 7, 9_10._Thiele, 1918:373.?MacNeil 1960:40, pi. 11: fig. 19. Argyropeda [sic] divina Melvill and Standen.?Shuto, 1969: 64-65, pi. 2: figs. 7-11. Cerithium (s. str.) spinigerum Martin, 1884:156, pi. 8: fig. 152. Potamides spimger (Martin).?Tesch, 1920:58, pi. 131: fig. 185. Potamides (Tympanolonus) spiniger (Martin).?Martin, 1899: 208. Argyropeda [sic] spinigera (Martin).?Shuto, 1969:64, pi. 2: figs. 7-11. DESCRIPTION.?Shell: small, about 7 mm long, thin, elongate, turreted, and consisting of 9 adult whorls with apical angle of 35?. Whorls convex, angulate, and deeply impressed suturally. Adult whorls sculptured with two primary spiral cords, one weaker spiral cord adjacent to suture on upper portion of whorl, and with 12-13 weak, transverse axial ribs that form sharp nodes where they cross the two marginal major spiral cords. Axial ribs and nodes stronger on earlier whorls, nearly absent on penultimate and body whorls. Suture deep and distinct. Protoconch I smooth, one and one-half whorls; protoconch II, two whorls, sculptured with spiral band of axially elongated pustules adjacent to suture and with two spiral cords near mid-portion of whorl. Spiral cords sometimes weakly pustulate. Sinusigera sinus deep and narrow. Transition from proto- conch to teleoconch sharply defined. Body whorl inflated, sometimes with varix opposite outer lip, especially in older shells. Sculpture on body whorl frequently diminished, and below the two pri- mary cords there are 5-6 smooth spiral cords that become thinner as they progress to siphonal canal. Aperture ovate, close to one-fourth the length of the shell. Anterior siphonal canal short and broad, slightly curved to left. Small, indis- tinct anal canal present. Outer lip thin, smooth, and sinuous in outline. Columella slightly con- cave to straight with thin shiny callus. Shell covered with thin, light tan periostracum, and is shiny and vitreous in recently dead specimens, chalky in older ones. Shell frequently pigmented with light tan flammules that run transversely between axial ribs. Portions of spiral cords be- tween axial ribs usually darker tan creating light spiral spots. Animal: Head and foot pigmented with dark brown, especially on snout and tentacles. Tenta- cles large, broad, and with large dark eyes at their bases. Snout broad, bilobed at tip, and with relatively large buccal mass. Mouth with pair of jaws about 0.25 mm long, triangular in shape, comprised of 55-60 rows of hexagonal plates that become quadrate at the cutting edge. Stomach filled with fine sand, foraminifera, and detrital SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY FIGURE 2.?Argyropeza divina Melvill and Standen: a,b, typical adult specimens showing overall sculptural pattern (USNM 238517, USBF Sta 5450, off Batan Id, Lagonoy Gulf, E Luzon, Philippines, 746m); c-e adult specimens (USNM 276553, USBF Sta 5242, Pujada Bay, E Mindanao, Philippines, 349m; c and e, 14X; d, 28X);/, side view of adult shell showing sinuous outer lip, (USNM 302513, USBF Sta 5191, Tanon Str, off Refugio Id, Philippines, 258 m, 14X); g, protoconch showing larval shell sculpture (USNM 238513, locality same as in a,b); h, detail of aperture showing anterior siphonal canal and sculpture of body whorl (USNM 276553, locality same as in c-e)\ i, protoconch showing sinusigera notch and larval shell sculpture, 200X (USNM 238517, locality same as in c-e);j, top view of protoconch showing change between larval and adult sculpture (USNM 238517, 200X, locality same as in c-e); k, detail of adult whorls showing two spiral cords and nodules (USNM 276350, USBF Sta 5247, off Davao, Mindanao, Philippines, 40X). NUMBER 321 TABLE 4.?Argyropeza divina, measurements of shell characters (in mm) character length width aperture length shell lenth aper. length # whorls it spiral cords t ribs apical angle number 20 20 20 20 20 20 20 20 mean 6.96 2.21 1.85 3.80 9.00 2.00 12.5 35? range 6.0-7.58 1.91-2.66 1.33-2.16 3.41-4.51 - - 12-13 - 3d 0.44 0.18 0.20 0.38 - - - - particles. Intestine large, filled with many ovate fecal pellets about 0.2 mm in diameter. Mantle edge papillate and slightly flaring at anterior siphon. Pallial gonoducts open. Other pallial or- gans not observed. Foot large, and with groove at anterior of propodium. Operculum thin, cor- neous, tan, nearly circular, and multispiral with subcentral nucleus. Operculum large in relation to foot, slightly concave and bent at circumfer- ence to fit aperture snugly. Attachment scar on reverse of operculum ovate. Eggs and larvae un- known. Radula (Figure 3): Radular ribbon taenioglos- sate, about one-eleventh the length of the shell, comprising 50 rows of teeth. Rachidian tooth quadrate, somewhat concave at sides. Cutting edge of rachidian with sharply pointed central cusp flanked with two, sometimes three smaller cusps on each side. Base of rachidian tooth flat with slight lateral projections at each end. Lateral tooth trapezoidal, laterally elongate and with slightly curved top. There are seven cusps, the first small, the second large and sharply pointed, and the remaining cusps becoming smaller to- ward the lateral portion of the cutting edge of the tooth. A blunt longitudinal projection extends from the lower mid-portion of the basal plate. Base of lateral tooth straight. Inner marginal tooth long, slender, and curved, pointed at tip and serrated with 4-6 sharp denticles on inner side and with 5-6 denticles on outer side. Outer marginal tooth same as inner but lacking denti- cles on outer surface. ETYMOLOGY.?Latin divinus ("divine"). COMPARATIVE REMARKS.?Argyropeza divina is distinguished from its congeners by a generally larger size, a deep sutural impression, sharply sloped whorls adjacent to the suture, and by sculpture of two strong spiral cords that are set with sharp nodes. The aperture length to shell length ratio is lower than in the other species and the aperture is decidedly more ovate. Although not noted in the original description, it is the only Argyropeza species that is pigmented with brown blotches. The rachidian tooth of the radula usu- ally has two small denticles adjacent to each side of the central cusp whereas in A. izekiana, there are normally three denticles on each side of the central cusp. Argyropeza divina is the type-species of the genus and appears to be the most common and abundant species in the group. Melvill and Standen (1901:872) compared it with Royella sinon Bayle (cited as Cerithiopsis sinon), but the sculp- tural resemblance is only superficial for Royella is a monotypic genus in the Potamididae H. and A. Adams, having a round, multispiral operculum with a central nucleus and a large shell, and is phyletically far-removed from Argyropeza. Schepman (1909:61) noted that the operculum is multispiral. Although there are numerous spi- rals, the nucleus is subcentral and cerithioid; consequently, the operculum should not be con- strued to be multispiral in the sense of a potami- did operculum. The radula of this species was crudely illustrated by Schepman (1909, pi. 21: fig. 3), who found it too small to accurately describe. The radular ribbon is very small: It averaged 0.9 mm in length and 0.18 mm in width and comprised 50 rows of teeth in two specimens from which I was able to extract it undamaged. Although Schepman (1909:169) said there were three smaller cusps adjacent to each side of the central cusp of the rachidian tooth, scanning electron micrographs show that there is variation in the number of cusps and that there are usually only two cusps present (see Figure 3). The inner and outer marginals are serrated with tiny cusps along their cutting edges. 10 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY FIGURE 3.?SEM micrographs of radula and operculum of Argyropeza divina (USNM 276350, USBF Sta 5247, off Davao, Mindanao, Philippines, 247m): a, portion of radular ribbon, 260X; b, close-up of half row of teeth showing tiny cusps on sickle-like marginal teeth, 420X; c, detail of rachidian tooth, 1600X; d, view of free surface of operculum showing spiral growth lines and eccentric nucleus, 50X. NUMBER 321 11 ECOLOGY.?Museum records indicate that A. divina normally occurs on muddy bottom throughout its range. It is occasionally found on very fluid mud or on fine sand substratum. Sta- tion data from 75 samples indicate a bathymetric range of 58-923 meters and a mean depth range of 356 meters. Specimens from the western Pacific tend to be larger than those from the western Indian Ocean. The stomachs of several specimens from the Philippines were filled with fine sand, detritus, and a few foraminifer tests. Fecal pellets were ovoid, about 0.2 mm in length and com- prised fine sand and detritus. The small radula and scythe-like lateral teeth indicate that A. divina ingests the sediment on which it lives and is probably a detritivore. GEOGRAPHIC DISTRIBUTION.?(Figure 4). This species occurs throughout the Philippines and the 6Oe Indonesian Archipelago, including New Guinea. It is also found in Madagascar and in eastern Africa, from Zanzibar to Durban, South Africa. Originally collected in the Gulf of Oman, it prob- ably occurs in suitable habitats throughout the Indian Ocean. Argyropeza divina is geographically sympatric with A. izekiana and A. schepmaniana in the Philippines and occurs with A. izekiana in New Guinea and in eastern Africa. All three species probably occur throughout the Indian Ocean and western Indo-Pacific Oceans. FOSSIL RECORDS.?Argyropeza divina has been re- corded as a fossil from the Pliocene of Okinawa (MacNeil, 1960:40, pi. 11: fig. 9). MacNeil re- marked that the fossils did not appear to be separable from living A. divina. I have examined his specimens and concur that the fossils are conspecific with A. divina. I have also seen Pleis- I4O?O" ttf to* 6O* 80? IOO? FIGURE 4.?Geographic distribution of Argyropeza divina Melvill and Standen. 12 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY tocene fossils deposited in the Australian Mu- seum, Sydney, from the NW bank of the Kavavas River, near Riet, Gazelle Peninsula, New Britain, Papua. Although Shuto (1969:65) noted that fossils he identified as A. divina from the Tertiary of Panay Id, Philippines differed slightly from typical A. divina in having a weakly granulated subsutural thread, I concur with him that they are probably conspecific. I believe Shuto (1969:65) was wrong in considering A. spinigera to be a valid species because examination of many specimens of A. divina shows that the arrangement of the basal spiral cords of A. spinigera falls within the range of variation of A. divina. I thus regard A. spinigera to be conspecific with A. divina. A fossil species from the Pliocene of Java, de- scribed by K. Martin (1884:156, pi. 8: fig. 152) as Cerithium spinigerum, appears to be conspecific with A. divina. Tesch (1920:58, pi. 31: fig. 185) erro- neously transferred C. spinigerum to the genus Potamides Brongniart, family Potamididae. His figures of the fossil specimens unequivocally de- pict Argyropeza divina. SPECIMENS EXAMINED.?ARABIAN SEA: Gulf of Oman, 285 m (USNM 424891). EASTERN AFRICA: Baia de Laurenco Marques, Mozambique, 450 m (USNM 718491); near Inhaca, Baia de Laurenco Marques, Mozambique, 366 m (USNM 717907); 60 mi (96.0 km) NE of Durban, South Africa, 366 m (USNM 717246); 30 mi (48.0 km) NE of Durban, South Africa, 77 m (USNM 718107). MADAGAS- CAR: 40 mi (64.0 km) WSW off Tulear, 82 m (USNM 717535; 717516; 717613); Tulear (coll. B. Thomassin). PHILIPPINES: Tayabas Bay, off Tayabas Lt, Luzon, 347 m (USNM 285464); Tayabas Bay, off Tayabas Lt, Luzon, 152 m (USNM 285545); Tayabas Bay, off Tayabas Lt, Luzon, 291 m (USNM 285617); Tayabas Gulf, Luzon, (USNM 301903); Balayan Bay, Luzon, 291 m (USNM 235360); Regay Gulf, off Arena Pt, Luzon, 525 m (USNM 284289); off Matocot Pt, W Luzon, 311 m (USNM 775069; USNM 775068); off Matocot Pt, W Luzon, 402 m (USNM 775036); off Malavatuan Id, W Luzon, 186 m (USNM 774765); off Cape Santiago, W Luzon, 720 m (USNM 235094); off N Cebu, 130 m (USNM 280890); off Lauis Pt, E Cebu, 302 m (USNM 288515); off Lauis Pt, E Cebu, 291 m (USNM 288740); off Lauis Pt, E Cebu, 296 m (USNM 290490); off Lauis Pt, E Cebu, 320 m (USNM 289140); off Chocolate Id, N Cebu, 271 m (USNM 280842; USNM 259603); off Batag Id, N Samar, 700 m (USNM 289381); Sogod Bay, Leyte, 918 m (USNM 277844); off Tolosa, E Leyte (USNM 277768); off Lusaran Lt, Guimaras, 175 m (USNM 281313); off Apo Id, S Negros, 468 m (USNM 291201); off Apo Id, S Negros, 464 m (USNM 286654); off Cabilao Id, W Bohol, 318 m (USNM 259839); off Ponson Id, Camotes Id, 347 m (USNM 298383); NW off Panglao Id (USNM 246937); off Pescador Id, Tanon Strait, 419 m (USNM 3925; USNM 281154); off Pescador Id, Tanon Strait, 548 m (USNM 274927); off Refugio Id, Tanon Strait, 472 m (USNM 302513); off Observatory Id, Palawan, 84 m (USNM 282594); W of Cape Melville, Balabac, 214 m (USNM 237927); Lagonoy Gulf, E Luzon, 914 m (USNM 787685); off Pt Tuguan, S Luzon 731 m (USNM 285409); off Sombrero Id, Balayan Bay (USNM 262305); off Som- brero Id, Balayan Bay, 291 m (USNM 262280; USNM 262309); off Sombrero Id, Balayan Bay, 216 m (USNM 774763); off Balanja Pt, SE Mindoro, 428 m (USNM 276250); off Pt Origon, Tablas, 133 m (USNM 281489); Regay Gulf, off N Burias, 192 m (USNM 312689; USNM 775113; USNM 280510); off N Ticao Id, 413 m (USNM 285275); off Pt Dumurug, Masbate, 249 m (USNM 284160); off Pt Dumurug, Masbate, (USNM 274690); offTalajit Id, SE Masbate, 245 m (USNM 298258; USNM 234204); off Adyagan Id, E Masbate, 245 m (USNM 775119); off Sibu- gay Id, E of Masbate, 247 m (USNM 277536); offDestacado Id, E of Masbate, 146 m (USNM 280585); offDestacado Id, 216 m (USNM 298062; USNM 285349); SE off Bantayan Id, 58.5 m (USNM 775050); off Cape Melville, Balabac Strait, 271 m (USNM 234741; USNM 297522); ofT Davao, Mindanao, 247 m (USNM 276350); Iligan Bay, N Min- danao, 923 m (USNM 290235); Pujada Bay, E Mindanao, 398.5 m (USNM 276497); Pujada Bay, E Mindanao, 313 m (USNM 276414); Pujada Bay, E Mindanao, 349 m (USNM 255602; USNM 276553); Pujada Bay, E Mindanao, 393 m (USNM 380152; USNM 277461); E of Bongo Id, 289 m (USNM 775058). BORNEO: Off Silungan Id, 558 m (USNM 279078; USNM 774761; USNM 774759); Sibuko Bay, Sipadan Id, 759 m (USNM 278704); Sibuko Bay, off Si Amil Id, 534 m (USNM 289713); Subuko Bay, offMabul Id, 475 m (USNM 278824). NEW GUINEA: 2 mi (3.2 km) S Konori Id, Mios Woendi Atoll, Padaido Ids, 457 m (ANSP 025362). Argyropeza izekiana Kuroda FIGURES 5-7 Argyropeza izekiana Kuroda, 1949:76-79, fig. 1 [holotype: NSMT; type-locality: off Tosa, Shikoku, Japan, 100 m]. Argyropeza izekti [sic] Kuroda.?Habe, 1964:42, pi. 12: fig. 27 [mistakenly cited as fig. 26]. DESCRIPTION.?Shell: small, about 4.6 mm long, elongate, turreted, comprising 8-11 whorls about 1.53 mm wide. There are 8 flat-sided adult whorls that are impressed suturally. Apical angle of shell NUMBER 321 13 35 degrees. Adult whorls with two spiral cords, one near top and the other at bottom whorl. Lower spiral cord sometimes weak. Spiral cords weakly beaded. One microscopic spiral cord on upper portion of whorl adjacent to suture. Shell sculptured with 12-14 axial ribs per whorl that form small sharp nodes where they cross spiral cords. Axial ribs strongest on first two whorls of teleoconch. Body whorl lacks axial ribs, nodes and has weak spiral sculpture. Suture well-de- fined, set off by sloping inferior and superior sutural ramp on each whorl. Protoconch I smooth, comprising one and one-half whorls; pro- toconch II, consists of two whorls, sculptured with spiral band of ovoid pustules adjacent to suture and with two spiral cords, the lower of which is formed of two fine, spiral lirae. Sinusigera sinus deep and narrow. Abrupt transition from proto- conch to teleoconch marked by distinct change in sculpture. Former varix normally on right dorsal side of body whorl. Sculpture of body whorl comprises two weak, widely-spaced, spiral cords below which are 4-5 spiral lirae that grow weaker as they approach the anterior siphonal canal. Aperture ovate-circular, a little more than one-fourth the length of the shell. Columella straight and with weak parietal callus. Anterior siphonal canal short and broad, opening to left about 45? from the shell axis. Outer lip convex, smooth, thin, slightly sinuous. Anal canal indis- tinct. Periostracum very thin, pale tan. Shell vitreous, shining, white, chalky in dead speci- mens. Operculum concave and with circumfer- ence slightly bent to fit snugly into aperture of shell. Animal (preserved): Head-foot small in relation to shell, flesh colored. Snout bilobed at tip. Ten- tacles wide, more flat than round, and each with large black eye at outer side of tentacle base. Intestine large, filled with large ovoid fecal pellets composed of fine sand. Anus close to mantle edge. Buccal mass large, filling much of snout. Radula (Figure 6): Radular ribbon long, tae- nioglossate. Rachidian tooth quadrate in shape, concave at sides, slightly convex at tip. Cutting edge of rachidian tooth serrated with long, sharply pointed central cusp that has a tiny lat- TABLE 5.?Argyropeza izekiana, measurements of shell char- acters (in mm) character length width aperture length shell length aper. length // whorls # spiral cords # ribs apical angle number 20 20 20 20 20 20 20 20 mean 4.63 1.53 1.09 4.27 8.00 2.00 12.5 35? range 4.17-5.25 1.42-1.75 1.0-1.25 3.86-4.67 ? - -? 12-13 - sd 0.29 0.12 0.84 0.23 - - - - eral denticle on each side of the median portion of cusp. Base of rachidian tooth slightly convex with sharp lateral projection at each side. Basal plate of rachidian tooth thick. Lateral tooth trap- ezoidal, laterally elongate and with slightly curved top that is serrated with 7-8 pointed cusps. First cusp small, second large, wide, and pointed, and remainder small and decreasing in size to- ward the lateral portion of tooth. Blunt longitu- dinal projection extends from lower mid-portion of basal plate. Base of lateral tooth slightly con- cave. Inner marginal tooth long, slender, curved, sharply pointed at tip, and serrated with 5-6 sharp denticles on inner side and 5 denticles on outer side. Outer marginal tooth same as inner marginal, but lacking denticles on outer surface. ETYMOLOGY.?Named in honor of Mr. Izeki. COMPARATIVE REMARKS.?This species is distin- guished from its congeners by 9.5 flat-sided, spi- nose whorls and by the presence of predominant transverse axial ribs that cross two weak spiral cords on each whorl. It is closest in sculpture to Argyropeza divina, which also has only two spiral cords per whorl and which is similarly spinose. Argyropeza izekiana is smaller and less attenuate than A. divina and has a shorter anterior siphonal canal than the latter species. The sutural ramp of A. izekiana is less pronounced than in A. divina. It should be noted that Habe (1964:42, pi. 12: fig. 27) mistakenly cited fig. 26 of his plate in reference to A. izekiana. He also erroneously as- 14 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY FIGURE 5.?Argyropeza izekiana Kuroda, showing variability in shell form and sculpture: a-c, apertural, side, and dorsal views of adult shells (note sinuous outer lip), 25X; d, protoconch showing larval shell sculpture, 170X; e, top view of protoconch showing disparity between larval and adult sculpture, 175X;/-A, apertural, side, and dorsal views of adult shells: note stronger axial riblets in contrast to a-c\ 30X; i-k, apertural, side and dorsal views of adult shells with strong axial ribs (USNM 262893, USBF 5131, off Panabutan Pt, W Mindanao, Philip- pines, 49m, 24X); /, protoconch showing sinusigera notch, 215X. (a-h and / all USNM 774591, USBF Sta 5398, off Gigantangan Id, NW Leyte, Philippines.) NUMBER 321 15 FIGURE 6.?SEM micrographs of radula and operculum of Argyropeza izekiana Kuroda (USNM 281893, USBF Sta 5392, off Adyagan Id, E Masbate, Philippines, 247m): a, worn portion of radular ribbon, 1000X; b, close-up of lateral and marginal teeth, 1500X; c, portion of radular ribbon, 650X; d, view of free portion of operculum, 100X. closer to the suture is erroneous. Bittium porcellanum Watson, 1886 is similar to this species. It looks very much like those morphs of A. izekiana that have prominent axial ribs, but signed it to the family Cerithiopsidae H. and A. Adams. Shuto's (1969:64) statement that A. izek- iana is readily distinguished from other Argyropeza species in having the upper row of pustules much 16 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY having examined the type-specimen, I regard B. porcellanum as distinct from A. izekiana. Moreover, the glossy shell with brown-tipped protoconch, and the depth at which it was collected (283 meters) indicate an assignment to a genus other than to Bittium. Watson (1886:559) was obviously uncomfortable in referring B. porcellanum to Bit- tium because he noted that it was an "aberrant form of Bittium." ECOLOGY.?This species lives at depths ranging from 49 to 914 meters and has a mean bathyme- tric distribution of 307 meters (Table 3). Station data show that it is usually found on sediments comprised of mud or finegrained sand. The small radula and fecal pellets that consist of fine sedi- ment and detritus point to a macrophagous feed- ing habit. Many specimens from the Philippines had drill holes that were moderately large and of the kind made by naticid snails (see Carriker and Yochelson, 1968). GEOGRAPHIC DISTRIBUTION (Figure 7).?Most records of A. izekiana are from the western central Pacific where it is found from southern Japan south to Indonesia, New Guinea, Australia, and east to New Caledonia and the New Hebrides. There is also a single record from Mozambique, in the western Indian Ocean. I have examined this material, which comprises three specimens, and find no essential differences in shell physiog- nomy between these specimens and those col- lected in the Philippines. Other Argyropeza species have a similar range and when more deep sea dredging occurs in the Indian Ocean it is proba- ble that A. izekiana will be found in other locali- ties. To my knowledge, no fossil records of this species exist. SPECIMENS EXAMINED?PHILIPPINES: off Matocot Pt, W Luzon, 384 m (USNM 277379); off Matocot Pt, W Luzon, 311m (USNM 275955; USNM 278514); off Matocot Pt, W Luzon, 402 m (USNM 774607; USNM 278474); off Matocot Pt, W Luzon, 314 m (USNM 277982); off Matocot Pt, W Luzon, 362 m (USNM 276725); off Matocot Pt, W Luzon, 247 m (USNM 276060); off Malavatuan Id, W Luzon, 186 m (USNM 258402; USNM 775111); off Lauis Pt, W Luzon, 296 m (USNM 774605); SW, off Corregidor Lt Luzon, 247 m (USNM 294331); SW, off Corregidor Lt Luzon, 216 m (USNM 278316); Lagonoy Gulf, E Luzon, 2(f i4