SMITHSONIAN MISCELLANEOUS COLLECTIONSVOLUME 122, NUMBER 10
Cfjarlea 9. anb Jfflarp Uaux ®BalcottEesiearcf) JftmbTWO SILICIFIEDCARBONIFEROUS TRILOBITESFROM WEST TEXAS(With 3 Plates)
BYHARRY B. WHITTINGTONMuseum of Comparative ZoologyHarvard University
(Publication 4146)
CITY OF WASHINGTONPUBLISHED BY THE SMITHSONIAN INSTITUTIONAPRIL 22, 1954

SMITHSONIAN MISCELLANEOUS COLLECTIONSVOLUME 122, NUMBER 10
CfjarleS S. anb Jftarp Uaux OTalcott
^esiearci) JftmbTWO SILICIFIEDCARBONIFEROUS TRILOBITESFROM WEST TEXAS(With 3 Plates)
BYHARRY B. WHITTINGTONMuseum of Comparative ZoologyHarvard University
PER\ /ore
(Publication 4146)
CITY OF WASHINGTONPUBLISHED BY THE SMITHSONIAN INSTITUTIONAPRIL 22, 1954
ZU Bovi (gaUimexi (pressBALTIMORE, MD., 0. S. -V
Charles ©. anb Jflarp "tTaux Wakott &e$eatd) JfunbTWO SILICIFIED CARBONIFEROUS TRILOBITESFROM WEST TEXASBy HARRY B. WHITTINGTONMuseum of Comparative ZoologyHarvard University(With Three Plates)The specimens of silicified trilobites described in the following pageswere collected and prepared by Dr. Arthur L. Bowsher, of the UnitedStates National Museum (hereafter abbreviated as U.S.N.M.). I amindebted to Dr. Bowsher for suggesting that I study this material andto Dr. G. Arthur Cooper for permitting the loan of it to me. All thespecimens are in the National Museum collections and are from thefollowing localities
:
U.S.N.M. locality 30/O.—Helms formation, El Paso quadrangle,Hueco Mountains, Tex., 2,\ miles west of Powwow Tanks, latitudeapproximately 3i°5o'i7" N., longitude io6°04'4o" W. This localityis stop 13 (p. 40), West Texas Geological Society Guidebook, FieldTrip No. 5, November 1949, and stop 1 on the map accompany-ing West Texas Geological Society Field Trip of May-June 1946.No. 3070-2 is from a limestone thought to be the same as bed 9, sec-tion "C" of 1946 Field Trip Guidebook, and No. 3070-4 is from alimestone thought to be the same as bed 1 1 of the same section.U.S.N.M. locality 3069.—Helms formation, El Paso quadrangle,Hueco Mountains, Tex., 1.1 miles west of Powwow Tanks, latitudeapproximately 3i°5o'i7" N., longitude io6°03'38"W. No. 3069-2 isfrom about 10 feet above the base of the Helms in the saddle, from anoolitic limestone lens, and approximately equivalent to the horizonof No. 3070-2. No. 3069-4 is from about 25-30 feet above the baseof the Helms in the saddle, from an oolitic limestone with Archimedes,and approximately equivalent to the horizon of No. 3070-4.The numbers of these localities are used in subsequent referencesto the specimens. The Helms formation in west Texas and adjacentNew Mexico has been described briefly by Laudon and Bowsher(1949, pp. 19-20, 31-34), and the term is used here in the restrictedSMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 122, NO. 10
2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122
sense of these authors. The Helms formation is stated by Laudonand Bowsher to be of Chester (Upper Mississippian) age, and it isof interest that the commonest trilobite in the formation, describedhere as Paladin (Paladin) helmsensis, new species, is very much likethe type species of the genus from the Morrow Series (Lower Penn-sylvanian) of Oklahoma.The silicified specimens show the morphology of the exoskeleton inunusual detail and perfection ; hence in the next section significantfeatures of morphology and development are described and discussed,and these comments are not repeated in the ensuing detailed descrip-tions. The terminology employed follows that of previous papers(Whittington, 1950, p. 533), except that I have used pleural regionof the pygidium rather than pleural lobes or side lobes of Warburg( 1925), and interpleural grooves rather than furrows. The additionalterms used in describing the articulation of the thorax, and the hypo-stome, are explained on plates 2 and 3.In order to avoid ambiguity in the terms "length" and "breadth" indescriptions, I have used (in the abbreviated form indicated in paren-theses) sagittal (sag.) to describe a measurement in the median line;exsagittal (exs.), parallel to, but outside of, the median line; andtransverse (tr.), at right angles to the median line.MORPHOLOGY AND DEVELOPMENT OF THE SILICIFIED SPECIESAn unusual feature of the silicified exoskeletons is the relativelygreat thickness, as compared, for example, to those of silicified Ordo-vician trilobites. I consider the thickness to be original and not aresult of the process of silicification. Plate 2, figures 5 and 6, and plate3, figures 3, 5, and 6, show the thickness of the exoskeleton at thesuture lines and along selected sections. The doublure of both py-gidium and cephalon is thicker than the immediately overlying dorsalexoskeleton (pi. 3, figs. 3, 5), nowhere more so than at, and adjacentto, the rostrum. The inner part of the thoracic pleurae is also thick,at a maximum at the posterior edge, the inner surface flat and slopingforward to the much thinner anterior edge. The thickness is suchthat there is no ridge on the inner surface corresponding to the pleuralfurrows on the outer surface (pi. 3, figs. 10, 13).Four pairs of glabellar furrows have been observed in some Car-boniferous trilobites (e.g., Stubblefield, 1948, p. 99; R. and E. Richter,1 95 1, pi. 5). On the inner surface of the exoskeleton (pi. 3, fig. 2)these furrows form inwardly projecting platforms with a well-definededge (cf. R. and E. Richter, 1951, p. 225). These are areas of muscle
NO. 10 TRILOBITES FROM WEST TEXAS—WHITTINGTON 3
attachment, as is also the thickened and projecting outer one-third ofthe occipital furrow. On the outer surface (pi. 3, fig. 1) only thefirst (basal) furrow appears as a depression, the second, third, andfourth furrows as smooth areas, in larger specimens appearing as con-spicuous dark patches, dark perhaps because the exoskeleton is thickerhere. The articulating furrows of the thoracic axis are slightly thick-ened at the extremity, and presumably are areas of muscle attachment.On the pygidial axis (pi. 3, fig. 5), however, the outer parts of thering furrows become shallower, and the ovate areas between them, ap-pearing darker in some specimens, are areas of muscle attachment.The eye surface (pi. 3, figs. 4, 6) is externally almost smooth, thefacets faintly convex. On the inner surface each circular facet isstrongly convex, and the facets are close-spaced and arranged in verti-cal and diagonal rows. The course of the cephalic sutures is revealedin detail (pi. 2, figs. 1, 5, 6; text fig. 1), and I am not aware of anyprevious descriptions of the rostrum of a Carboniferous trilobite. Theedge of the exoskeleton at the sutures is thick and flat, and the hypo-stome fits against both the posterior edge of the rostrum and the ad-jacent inner edge of the doublure. The wing process (at the tip ofthe large anterior wing) evidently rested in the conspicuous circularpit in the anterior boss on the inner surface of the cranidium (pi. 3,fig. 17). Thus the hypostome was attached to the rest of the cephalonin the same manner as in calymenids, cheirurids, and other trilobites.Articulation between the segments of the thorax and the cephalonand pygidium is effected by a series of devices (see pi. 3, figs. 7-13,15, 16, and compare Whittington and Evitt, 1954, pp. 21-24). Thering process is a large boss situated at the outer, posterior edge of theaxial ring, and fits into a ring socket at the anterior, outer edge. Abovethe ring socket, in line with the axial furrow, is a tiny, round axialprocess, which fits into the axial socket in the posterior edge of thesegment at the base of the ring process. A narrow (exs.) strip alongthe anterior edge of the inner part of the pleura is defined by a shallowfurrow, and the leading edge is thin and bluntly rounded. It fits intoa groove in the thick posterior edge of the inner part of the pleura,this groove being beneath the upper, outer margin of the pleura. This
"tongue and groove" articulation extends out to the fulcrum, whereit dies out, and there are no articulation processes and sockets at thefulcrum. The posterior edge of the cephalon inside the branches ofthe facial suture, and the anterior margin of the pygidium inside thefulcra, are shaped like the corresponding edges of the thoracic seg-ments. The outer parts of the thoracic pleurae, and the pygidium, arefaceted to facilitate overlap in enrollment. In the doublure of each
4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122
segment is a broad V-shaped notch (pi. 3, fig. 14), the Panderianopening, and the anterior edge of this notch is raised (inwardly pro-jecting), and acts to limit the amount of overlap between segments.Only what are probably the later meraspid stages of the develop-ment are known (pis. 1, 2). The cranidium shows a general reduc-tion in convexity with increasing size. The glabella in the smallestspecimens is almost parallel-sided, and with increasing size the lateralexpansion of the anterior lobe takes place, the posterior part widensbetween the eye lobes, and the relative convexity of the posterocentralglabellar region, and of the basal glabellar lobes, is reduced. The eyelobe becomes relatively shorter. The pygidium shows a considerablereduction in convexity with increasing size, and the shallow mediannotch in the posterior margin of small specimens soon disappears.The meraspid development of Ditomopyge was described by Weller(1935), and the smallest cranidium, 1 mm. in length, has tne sub-parallel-sided glabella, long (sag.) anterior border and eye lobe seenin Paladin. However, the glabellar lobation is absent, in contrast tothe presence of well-marked basal lobes and furrows in Paladin.Small pygidia of Ditomopyge show a median notch in the posteriorborder (Newell, 1931, pi. 31, fig. 31 ; Weller, 1935, p. 508) like thatseen in Paladin. While the development of the pygidium in the twogenera has some features in common, a notable difference is that inDitomopyge the pleural regions increase in convexity (Weller, 1935,figs. 4c, 5c, 7c, 8c), in contrast to the decrease in Paladin.The meraspid specimens of Paladin do not resemble any geologicallyolder adult Carboniferous trilobite, and Weller (1935, p. 513) like-wise found that the meraspid specimens of Ditomopyge resembled noknown geologically older adult trilobite. One may take these observa-tions as further evidence of the untruth of the so-called "law" of re-capitulation, in the strict sense of Haeckel (cf. de Beer, 1951).SYSTEMATIC DESCRIPTIONSFamily PROETIDAE (Hawle and Corda, 1847), Salter, 1864Subfamily PHILLIPSIINAE (Oehlert, 1886), Pfibyl, 1946A characterization of this subfamily has recently been given byPfibyl (1946, pp. 33-34). The present material of Paladin shows thatup to four pairs of glabellar furrows may be present. Few illustra-tions have been published of phillipsiinid hypostomes, but those avail-able (e.g., Woodward, 1883-1884; Weber, 1937) suggest that theyare similar to each other and like that of Paladin (pi. 1, figs. 29, 30,35 ; pi. 2, figs. 21, 26, 27, 32, 33). Characteristic are the large anterior
NO. 10 TRILOBITES FROM WEST TEXAS—WHITTINGTON 5
wings, lack of distinct anterior border, narrow lateral, but wider(sag.) posterior, border, and short (sag.), crescentic, inflated posteriorlobe of the middle body. This type of hypostome is not like knownexamples of hypostomes (Pfibyl, 1947, figs. 12-15, 17-19) of proetidgenera in other subfamilies, and may be typical of the Phillipsiinae.The shape of the rostrum may equally well be characteristic of thesubfamily, but little information is available.
Genus PALADIN Weller, 1936Type species.—Griffithides morrozvensis Mather, 191 5, by originaldesignation of Weller, 1936, p. 707.Discussion.—The most abundant of the two species of silicifiedtrilobites described below has been compared with the holotype ofPaladin morrozvensis, and belongs in this genus. The second speciesdiffers from the first notably in the greater convexity of the cephalonand pygidium, the shorter anterior cephalic border, and the outline ofthe glabella, which is less expanded between the eye lobes but morestrongly expanded anteriorly. These relatively minor differences allyit with Kaskia chesterensis (Weller, 1936, pp. 708-711, pi. 95, figs.4a-6), the type of the genus Kaskia Weller, 1936. K. chesterensis hasan even shorter (sag.), steeper anterior border. Weller admitted(1936, p. 708) that Paladin and Kaskia were closely similar, and thatthere were species intermediate between typical species of the twogenera. The second silicified species here described is one of theseintermediates. In view of these facts, it seems to me preferable toregard Kaskia as a subgenus of Paladin, with P. morrozvensis repre-senting the typical subgenus Paladin (Paladin), and this procedurehas been followed below.Reed (1942, pp. 653, 660-667, pi. 10, figs. 4.5b, pi. 11, figs. i-5a;1943, pp. 179-184, pi. 2, figs. 6, 7, pi. 3, figs. 1-8) considered thatthe forms he referred to his genus Weberides included most of, if notall, the originals of Woodward's (1883-1884) plate 4, and were similarto the Russian species described by Weber (1933, pp. 33-35, 37-4 1 ,pi. 2, figs. 2-1 1, 17-33, 36-41, text figs. 14-17, 19-21 ; 1937, pp. 74-75,pi. 8, figs. 31-34, 36, 39-44, 48) under the names Griffithides lutuginiand varieties and G. transilis and varieties. Weller (1936, pp. 707-708), however, had previously placed these Russian species and va-rieties in his genera Paladin and Kaskia. Reed recognized this (1943,p. 180) but did not say how Weberides differed from Paladin. Itseems that some of the species referred to above may be congeneric,and if so ought to be placed in Paladin. Before it is concluded that
6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122Weberides Reed, 1942, is a synonym of Paladin, however, the diplo-type of Weberides should be reexamined, for Reed (1942, p. 663)admits that he did not see it. The specimen in question (original ofM'Coy, 1844, pi. 4, fig. 5) is a pygidium, with a short, blunt spine onthe posterior border.The genus Ditomopyge Newell, 1931 (as emended by Weller, 1935)is related to Paladin (Kaskia), as Weller pointed out (1936, p. 711).The inflation of the central region of the glabella in front of the occi-pital ring seen in P. (K.) rarus, new species, could give rise to thepreoccipital lobe of Ditomopyge. The free check of P. (K.) rarus,new species, is much more like that of Ditomopyge than that of P.(P.) helmsensis, new species, which lacks the flattened upper surfaceof the border. Contrary to the opinion of Weller (1936, pp. 713-714),I regard Ameura as related to Paladin. I have examined the holotypeof Ameura sangamonensis (Meek and Worthen, 1865) and the gla-bella is only slightly wider between the eye lobes than across the an-terior lobe. The basal glabellar lobes do have independent convexity.The pygidium, of length (sag.) about equal to width, recalls theoriginal of Woodward's (1883-1884) plate 4, fig. 9, and the elongatedappearance is distinctive.The aforementioned four genera, together with Sevillia (Weller,1935, p. 506, explanation of text fig. 9, nomen nudum; Weller, 1936)and Linguaphillipsia Stubblefield, 1948, probably form a related groupranging from Lower Carboniferous to Lower Permian in age, wide-spread in North America and Eurasia.PALADIN (PALADIN) MORROWENSIS (Mather, 1915)Plate 1, figures 1-6, 9Holotype.—Walker Museum No. 16174, incomplete cephalon, fromBrentwood limestone, Morrow Series, lower Pennsylvanian, SawneyHollow, head of Indian Creek, Okla., and 3^- miles south of Evansville,Ark.Description.—The holotype is refigured here, and the followingnotes are added to supplement Mather's (1915, pp. 244-246, pi. 16,figs. 13, 13a) original description. Basal glabellar furrow deepest atabout the midlength, disappearing before reaching axial furrow. Ad-ditional furrows not represented by depressions in outer surface. An-terior branch of facial suture running at first outward at about 50 tothe sagittal line, then on the border, opposite the maximum width ofthe anterior glabellar lobe, curving to run inward straight to the mar-gin. The angle between the two sections is about ioo°. The doublure
NO. 10 TRILOBITES FROM WEST TEXAS—WHITTINGTON 7
of the cephalon is convex and slopes steeply laterally, but is flattenedand slopes gently anteriorly. The rostral suture runs close to the outeredge, the connective sutures curve inward, and the hypostomal sutureruns in a curve convex forward. The rostrum is thus similar in outlineto that of P. (P.) helmsensis, new species.The associated pygidium is also refigured, and the border is gentlyconvex, not concave as stated by Mather (1915, p. 245).PALADIN (PALADIN) HELMSENSIS Whittington, new speciesPlates 2, 3; text figure 1Holotype.—U.S.N.M. No. 116513, cranidium, original of plate 2,figures 1, 2, 5, 6 ; locality 3070-2.Paratypes.—U.S.N.M. Nos. n65i4a-h; free cheek, rostrum, andhypostome from locality 3070-2 ; two segments from locality 3069-4
;
two segments from locality 3070-4 ; pygidium from locality 3069-2.Description.—Dimensions of holotype in millimeters: Length (sag.)7.0, height 2.7; length of glabella (sag.) 6.3, width across anteriorlobe 3.9, at third furrows 3.1, of occipital ring 3.9. Length of para-type pygidium (sag.) 6.3, width 7.8, height 2.8. Cephalon subsemicir-cular in outline, gently convex. Glabella gently convex (sag. and tr.),outlined by shallow axial and preglabellar furrows ; narrowing slightlyimmediately in front of the occipital ring, expanding between the eyelobes, then narrowing again forward to the minimum width oppositethe third furrows, and then expanding forward again until widthacross anterior lobe is the same as, or slightly greater than, that of oc-cipital ring. Latter moderately convex, highest point near posteriormargin, from which it slopes down to the shallow, sinuous occipitalfurrow ; faint median tubercle. Four pairs of glabellar furrows (pi.3, figs. 1, 2), the first (basal) appearing as shallow depressions, gentlycurved, directed inward and backward to isolate triangular, gently con-vex basal lobes. The basal furrows are deepest at midlength, becomingpoorly defined at the outer extremity, faint at the inner ends as theymeet the occipital furrow. The maximum width of the basal lobes isone-third the glabellar width in front of the occipital furrow. Betweenthe basal lobes the central glabellar region is slightly inflated and pos-teriorly slopes steeply. The second and third glabellar furrows areprogressively shorter and directed less strongly backward, the fourthshort, ovate, directed slightly forward and commencing a short dis-tance inside the axial furrows. Cheeks sloping gently outward andforward, with a broad (tr.) lateral border defined by the slightchange in slope at the faint border furrow, the anterior border nar-
8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122
rower (sag.). Posterior border defined by a deep border furrow, andwith independent convexity. Genal spine broad at base, relativelylong. Eye lobe large, length (exs.) more than one-third that ofcephalon, situated with the anterior edge about opposite the glabellarmidpoint, and close to the axial furrow, the highest point lower thanthe glabellar midline between the eye lobes. Palpebral lobe withoutrim, outer part horizontal, inner part sloping down to axial furrow.Eye surface (pi. 3, figs. 4, 6) with numerous small, gently convexfacets. Anterior branch of suture runs straight outward and forwardfrom the eye lobe onto the border, then curves and runs straight in-ward and forward to reach the anterior margin at a point in line(exs.) with the inner margin of the eye lobe. The posterior branchruns outward and backward to the border furrow, then curves, at firstmore strongly outward, over the posterior border to reach the marginjust inside the base of the genal spine. Doublure laterally of less width(tr.) than the border, gently convex and sloping steeply outward. An-teriorly doublure becomes flattened, horizontal, and narrower (sag.).The rostral suture runs along the outer edge of the doublure, the con-nective suture in a curve convex outward. The anterior and posteriormargins of the rostrum are thus forwardly curved, the lateral marginsoutwardly so. The rostrum (pi. 2, figs. 40-42) is also thickest alonga line midway between the anterior and posterior margins, so thatwhile the outer surface is flat, the inner is convex. The doublure ofthe free cheek adjacent to the rostrum shows a corresponding thicken-ing, which fades out laterally. Certain features displayed by the innersurface of the cephalon have been discussed above. Plate 3, figure 2,shows the doublure of the occipital ring. In the inner edge of thedoublure of the free cheek (pi. 3, fig. 6) is a shallow notch, in linewith the posterior border. I interpret this notch as the Panderian open-ing, and as corresponding with the larger notches in the thoracic pleu-ral doublures.Length of hypostome (pi. 2, figs. 21, 26, 27, 32, 33) (sag.) slightlygreater than maximum width across anterior wings. Middle bodygently convex longitudinally, more strongly so transversely, not de-fined anteriorly or separated from the anterior wings by a furrow,but laterally and posteriorly outlined by the change in slope at theborders. The crescentic posterior lobe, the tips at about two-thirds thelength of the middle body and opposite the lateral shoulders, has afaint independent convexity, most marked at the tips. The anteriorsutural edge of the hypostome is thick, extending between the basesof the wings, and fits against both the inner edge of the rostrum andthe doublure of the free cheeks (text fig. 1). The anterior wings are
NO. 10 TRILOBITES FROM WEST TEXAS—WHITTINGTON 9broad (exs.) at the base, slope steeply upward, with a small articulat-ing boss at the outer, anterior corner. The lateral borders narrow,gently convex, shoulder well marked, posterior border broader, mar-gin sinuous, posterolateral corners rounded. The interior view showsthat the doublure is narrow along the lateral borders, wider along theposterior border, and the furrow dividing the middle body more evi-dent. In lateral view the notch between shoulder and anterior wingis seen, and posterior wings seem not to be developed.
Fig. I.
—
Paladin (Paladin) helmsensis, new species. Outline reconstruction of theexoskeleton of the cephalon in ventral view, approximately X 7-Number of thoracic segments unknown. Axis moderately convex,each ring subdivided into a short (sag.) anterior part that disappearslaterally, and a longer (sag. and exs.) posterior part. The articulatingfurrow narrow and deep, the half-ring short (sag. and exs.). Innerpart of pleura horizontal, outer part bent steeply down, faceted, thefacet of the anterior segments (pi. 3, figs. 10-13) abruptly cutting offthe narrow (tr.) outer pleural part. The narrowness of these latterenables these segments to fit between and under the genal spines ofthe cephalon. Succeeding segments (pi. 3, figs. 7-9, 15, 16) have theouter pleural parts wider (tr.). Pleural furrow narrow and deep,situated at about half the length (exs.) at the fulcrum, and extendingto the inner edge of the facet. The interior view (pi. 3, fig. 10) shows
IO SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122
the doublure of the axial ring and the low ridge, the area of muscleattachment, formed by the outer part of the articulating furrow. Thedevices which facilitate articulation between the segments have beendescribed above. In the doublure of the outer pleural part (pi. 3, fig.14) is the broad notch of the Panderian opening. The doublure infront of, and outside, this notch is gently convex.Pygidium moderately convex, axis moderately convex and gentlytapering. In largest specimens 17 ring furrows, the inner part straight,deep, the outer shallow, turning slightly back. Inner, anterior part ofpleural region horizontal, outer part gently convex, steeply sloping,border distinctly separated by change in convexity, and sloping out-ward. Ten deep pleural furrows in largest specimens, progressivelymore strongly backwardly directed, ending at inner edge of border.Interpleural grooves faint, sometimes absent, sometimes first five visi-ble, not extending on to border. Doublure of same width as border,inner part bent steeply up.External surface of glabella and palpebral lobes with shallow, ir-regular pits (pi. 3, fig. 1 ) , largest near the median line. Small tuberclesoccur along the posterior edge of the occipital and axial rings. Raisedlines, parallel to each other and the margin, on the outer part of thecephalic and pygidial borders and the outer surface of the doublures.Hypostome with similar lines on the middle body and borders, andtiny, shallow, scattered pits on the middle body.Discussion.—Comparison of the cephalon of Paladin (Paladin)morrowensis with the type of P. (P.) helmsensis shows that the latterdiffers from the former principally in characters of the glabella. Thatof P. (P.) helmsensis is less inflated (as seen in longitudinal profile),has the basal glabellar lobes and posterior part of the central glabellarregion less inflated, and has the anterior lobe less expanded trans-versely, though between the eye lobes the glabella of P. (P.) helmsen-sis is more markedly expanded than that of P. (P.) morrowensis. Theexternal surface of the glabella and palpebral lobes is tuberculate inP. (P.) morrowensis, pitted in P. (P.) helmsensis. The lateral ce-phalic border of P. (P.) morrowensis slopes more steeply than thatof the Texas species. The pygidia of the two species (pi. 1, figs. 4-6;pi. 2, figs. 9, 10, 14, 15) are similar, that of P. (P.) helmsensis beingdistinguished by the axis showing more rings and being more inflatedposteriorly, and by the border being relatively broader (sag.) pos-teriorly. The axial rings of P. (P.) morrowensis are apparently with-out the row of tubercles on the posterior margin. Evidently P. (P.)helmsensis and P. (P.) morrowensis are closely related species, thoughthey differ considerably in age.
NO. IO TRILOBITES FROM WEST TEXAS—WHITTINGTON IIdevelopment of Paladin (Paladin) helmsensis, new speciesCranidium.—Length of smallest cranidium (pi. 2, figs. 34-36)(sag.) 1.5 mm., glabella narrowest between the anterior end of theeye lobes, but since it lacks the anterior and posterior expansions oflarger forms it appears almost parallel-sided. Basal glabellar furrowsdeep and broad, so that the basal lobes are prominent, and the posteriorpart of the central glabellar region is quite strongly inflated. The sec-ond and third glabellar furrows are ill-defined patches on the exo-skeleton. Length of anterior border of the cranidium (sag.) about one-eighth that of the glabella. Length of palpebral lobes (exs.) more thanone-third that of cranidium. In cranidia of increasing size that partof the glabella in front of the third furrow becomes relatively wider(compare figs. 1 and 34, pi. 2). The palpebral lobes become relativelysmaller, the length (exs.) being reduced to less than one-third that ofthe cranidium. The basal glabellar furrows become shallower, and theconvexity of the basal lobes and posterior part of the central glabellarregion is reduced. Small cranidia with close-spaced tubercles on theglabella and palpebral lobes, the tubercles on the frontomedian glabel-lar lobe close-spaced and arranged in lines subparallel to the anteriormargin. With increasing size of the cranidium these tubercles becomeless prominent, and in the largest cranidia only the reticulate patternof pits remains.The smallest hypostome known (pi. 2, figs. 39, 44) is little differentfrom the largest—the shoulders are rather more prominent, and thetips of the crescentic posterior lobe of the middle body are morestrongly inflated. The smallest pygidium known (pi. 2, figs. 37, 38,43) is 1.6 mm. in length (sag.), 2.2 mm. in width. Axis of 15 rings.Pleural region convex, inner, anterior part horizontal, outer partsteeply sloping, the border sloping outward but less steeply. Elevenpleural furrows visible, terminating at the inner margin of the border.First three interpleural grooves shallow, situated close to the succeed-ing pleural furrows, and extending on to the inner part of the border.Border broad (sag.) posterolaterally, narrow (tr.) anterolaterally,with a shallow median notch in the posterior margin. With increasingsize the pygidium maintains about the same ratio between length andwidth, and the original of plate 2, figures 30, 31, is 2.2 mm. in length(sag.), 3.3 mm. in width. The convexity of the pleural regions ismarkedly reduced, the notch in the posterior margin disappears andthe difference in the width of the border laterally and posteriorly isreduced. In a pygidium (sag.) 3.2 mm. long only the first interpleuralgroove is visible. The tubercles on the median part of the axial ringsare visible in this and larger specimens.
12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122PALADIN (KASKIA) RARUS Whittington, new speciesPlate i, figures 7, 8, 10-35Holotype.—U.S.N.M. No. 116511, cranidium, original of plate 1,figure 7, 8, 10, 11, locality 3070-4.Paratypes.—U.S.N.M. Nos. n65i2a-c, free cheek and pygidiumfrom locality 3070-2, hypostome from locality 3069-4.Description.—Length of holotype cranidium 5.6 mm., height 3.2mm. ; length (sag.) of glabella 5.1 mm., width across anterior lobe 3.6mm., between anterior ends of palpebral lobes 2.9 mm., of occipitalring 3.2 mm.The cephalon of this species is similar to that of Paladin {Paladin)helmsensis, new species, but is distinguished by (1) the greater con-vexity ; (2) the glabella being slightly expanded between the eye lobes,but more strongly expanded across the anterior lobe; (3) the sharperangle in the course of the anterior branch of the facial suture on theborder (compare the antero-lateral margins of the cranidia in pi. 1,fig. 7, and pi. 2, fig. 1) ; (4) the relatively shorter (sag. and exs.) an-terior border 5(5) the much greater change in slope at the border fur-row of the free cheek, resulting from the inner part of the borderbeing flattened. Additional ways in which the cephalon of P. (K.)rams differs from that of P. (P.) helmsensis are: (6) the basal gla-bellar furrows are deeper, the basal lobes more inflated; (7) the pal-pebral lobes are narrower (tr.) ; (8) the middle body of the hypo-stome is more convex, with deeper middle furrows, and tiny maculaeare present. There is a sharper angle in the anterior margin betweenwhere the hypostome fits against the rostrum and the doublure of thefree cheek, the shoulders are more prominent, and the posterior bor-der has the three blunt spines ; (9) the external surface of the gla-bella and palpebral lobes is tuberculate rather than pitted.Rostrum and thorax unknown.Length of paratype pygidium (sag.) 5.0 mm., width 6.9 mm.,height 3.0 mm. This pygidium is distinguished from that of P. (P.)helmsensis by the greater convexity and consequent height. Both theaxis and the pleural regions inside the border are more convex in P.(K.) rams, and the border slopes more steeply outward. The numberof axial rings and pleural furrows is the same in the two species, butthe ribs between the furrows in P. (K.) rams are much more convex.Discussion.—Paladin (Kaskia) rams is distinguished from the typespecies P. (K.) chesterensis (Weller, 1936, pp. 708-711, pi. 95, figs.4a-6), also of Chester age, by the less steep slope of the anterior partof the glabella and the longer (sag.) projecting anterior border (com-
NO. 10 TRILOBITES FROM WEST TEXAS—WHITTINGTON 13pare pi. i, fig. 10, with Weller, 1936, pi. 95, fig. 4c). The pleuralregions of the pygidium of the Texas species appear to be more convexthan those of P. (K.) chest erensis. Four pairs of glabellar furrowsare present in P. (K.) rarus, but only three are described as present inP. (K.) chesterensis.Weller (1936, pp. 708-710) pointed out that forms intermediatebetween the type species of Paladin (Paladin) and Paladin (Kaskia)occur. In the outline and convexity of the glabella, P. (K.) rarus ismore like P. (P.) morrowensis than is P. (P.) helmsensis, a furtherillustration of the close relationship between these species.
development of Paladin (Kaskia) rarus, new speciesThe smallest cranidium (pi. 1, figs. 23, 24) is 3.2 mm. in length(sag.). Compared with the largest cranidium it is more convex as awhole, as well as considering the frontomedian and basal glabellarlobes separately ; the glabella is less expanded anteriorly, and the pal-pebral lobes are longer. The development thus parallels that of Paladin(Paladin) helmsensis, with an expansion of the glabella anteriorly, ageneral reduction in convexity, and decrease in size of the palpebrallobes. The smallest pygidium (pi. 1, figs. 26-28) is 1.7 mm. in length(sag.), strongly convex, the outer parts of the pleural regions over-hanging the border. There are 13 or 14 axial rings, 10 pleural furrows,no interpleural grooves. There is no median notch in the posteriormargin of the border. The chief change with increasing size of thepygidium is the reduction in convexity, so that the outer parts of thepleural regions slope steeply but do not overhang the border.REFERENCESde Beer, G. R.195 1. Embryos and ancestors. Rev. ed. Oxford.Laudon, L. R., and Bowsher, A. L.1949. Mississippian formations of southwestern New Mexico. Bull. Geol.Soc. Amer., vol. 60, pp. 1-87, 44 figs.Mather, K. F.1915. The fauna of the Morrow group of Arkansas and Oklahoma. Bull.Sci. Lab. Denison Univ., vol. 18, pp. 59-284, 16 pis., 5 figs.M'Coy, F.1844. A synopsis of the characters of the Carboniferous limestone fossils ofIreland, viii+207 pp., 29 pis. Dublin.Newell, N. D.1 93 1. New Schizophoriidae and a trilobite from the Kansas Pennsylvanian.Journ. Paleont., vol. 5, pp. 260-269, 1 pi.
14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122
Pribyl, A.1946. Notes on the recognition of the Bohemian Proetidae (Trilobitae).Bull. Int. Acad. Tcheque Sci., 46th year, No. 10, pp. 1-41, 4 pis.1 fig.1947. Aulacopleura and the Otarionidae. Journ. Paleont, vol. 21, pp. 537-545, 1 pi., 19 figs.Reed, F. R. C.1942. Some new Carboniferous trilobites. Ann. Mag. Nat. Hist., ser. 11, vol.9, pp. 649-672, 4 pis.1943. Some Carboniferous trilobites from Scotland. Ann. Mag. Nat. Hist.,ser. 11, vol. 10, pp. 176-186, 2 pis.Richter, R., and Richter, Emma.1951. Der Beginn des Karbons im Wechsel der Trilobiten. Senckenbergiana,vol. 32, Nos. 1-4, pp. 219-226, 5 pis., 10 figs.Stubblefield, C. J.1948. Carboniferous trilobites from Malaya. Appendix to "Malayan LowerCarboniferous Fossils," by H. M. Muir-Wood, pp. 1-118, 17 pis., 3figs. British Museum (Natural History), London.Warburg, Elsa.1925. The trilobites of the Leptaena limestone in Dalarne. Bull. Geol. Inst.Uppsala, vol. 17, pp. 1-446, 11 pis.Weber, V.!933- Trilobites of the Donetz Basin. Trans. United Geol. and Prosp. Serv.U.S.S.R., fasc. 255, pp. 1-95, 3 pis., 33 figs.l 937- Trilobites of the Carboniferous and Permian system of U.S.S.R.Centr. Geol. and Prosp. Inst., Paleont. of U.S.S.R. Mon., vol. 71,fasc. 1, pp. 1-160, 11 pis., 78 figs.Weller, J. M.1935. Adolescent development of Ditomopyge. Journ. Paleont., vol. 9, pp.503-513, 3i figs.1936. Carboniferous trilobite genera. Journ. Paleont., vol. 10, pp. 704-714,1 pi.Whittington, H. B.1950. Sixteen Ordovician genotype trilobites. Journ. Paleont., vol. 24, pp.531-565, 8 pis., 9 figs.Whittington, H. B., and Evitt, W. R.1954. Silicified Middle Ordovician trilobites. Geol. Soc. Amer., Mem. 59,137 PP., 33 pis., 27 figs. (Dated Dec. 18, 1953.)Woodward, H.1 883-1 884. A monograph of the British Carboniferous trilobites, pp. 1-86,10 pis., 8 figs. Palaeontographical Society, London.
NO. IO TRILOBITES FROM WEST TEXAS—WHITTINGTON 15EXPLANATION OF PLATESPLATE 1 PageFigs. 1-6, 9.
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Paladin (Paladin) morrowensis (Mather) 61, 2, 3, Dorsal stereograph, left lateral, and anterior views of holo-type, Walker Museum No. 16174, X 3- 4, 5, 6, Dorsal stereograph,posterior, and right lateral view of pygidium, Walker Museum No.16174, X 3- 9, Ventral view of cephalic doublure of holotype, posi-tion of left (right in picture) edge of rostrum dotted, X 7i- Brent-wood limestone, Morrow Series, lower Pennsylvanian, Sawney Hol-low, head of Indian Creek, Okla., and 3! miles south of Evansville.,Ark.Figs. 7, 8, 10-35.
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Paladin (Kaskia) rams Whittington, new species 127, 8, 10, 11, Dorsal stereograph, interior, right lateral, and anteriorviews of holotype cranidium, U.S.N.M. No. 116511, locality 3070-4,X 3- 12, 13, 14, Dorsal stereograph, posterior, and left lateral viewsof paratype pygidium, U.S.N.M. No. 116512a, locality 3070-2, X 3-15, 18, Anterior view, dorsal stereograph of cranidium and freecheek, locality 3070-2, X 3- 16, 17, Dorsal and posterior views ofpygidium, locality 3070-2, X 3- 19, Right lateral view of cranidium,original of figures 15, 18, X 3- 20, 21, 22, Dorsal, posterior, and ven-tral views of pygidium, locality 3070-2, X 3- 23, 24, Dorsal and rightlateral views of cranidium, locality 3069-2, X 3- 25, 31, Left lateraland dorsal views of paratype free cheek, U.S.N.M. No. 116512b,X 3- 32, Interior view of same, X 10, locality 3070-2. 26, 27, 28,Dorsal, posterior, and left lateral views of pygidium, locality 3070-2X 4- 29, 30, 35, Ventral, interior, and left lateral views of paratypehypostome, U.S.N.M. No. 116512c, locality 3069-4, X 3- 33, 34, Ven-tral and left lateral views of hypostome, locality 3069-2 X 3- Helmsformation, Chester Series, upper Mississippian, Hueco Mountains,west Tex. Locality numbers are explained on page 1.PLATE 2Paladin (Paladin) helmsensis Whittington, new species1, 5, 6, Dorsal stereograph, anterior view, anterolateral stereographof holotype cranidium (U.S.N.M. No. 116513), and paratype freecheek (U.S.N.M. No. 116514a), locality 3070-2, X 3- 2, Left lateralview of holotype cranidium, U.S.N.M. No. 116513, locality 3070-2,X 3- 3, 4, Dorsal and left lateral views of free cheek, locality 3069-4,X 3- 7, 8, Dorsal and right lateral views of cranidium, locality3069-4, X 3- 9, 10, 14, 15, Dorsal stereograph, interior, posterior, andright lateral views of paratype pygidium, U.S.N.M. No. 116514b,locality 3069-2, X 3- n, 12, Dorsal and right lateral views of cra-nidium, locality 3069-4, X 3- I 3, 20, Dorsal and posterior views ofpygidium, locality 3069-2, X 3- 16, 17, Dorsal and right lateralviews of cranidium, locality 3069-4, X 3- 18, 19, Dorsal and pos-terior views of pygidium, locality 3069-4, X 3- 21, 26, 27, Rightlateral, ventral, and interior views of paratype hypostome, U.S.N.M.No. 116514c, locality 3070-2, X 3- S = shoulder; n = lateral notch.
l6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122
Page22, 23, Dorsal and right lateral views of cranidium, locality 3069-4,X 3- 24, 25, Dorsal and posterior views of pygidium, locality 3069-4,X 3- 28, 29, Dorsal and right lateral views of cranidium, locality3069-4, X 7i- 30, 31, Dorsal and posterior views of pygidium, lo-cality 3069-4, X 3- 32, 33, Ventral and right lateral views of hypo-stome, locality 3069-2, X 3- 34, 35, 36, Dorsal, right lateral, and an-terior views of cranidium, locality 3069-2, X 7&- 37, 38, 43, Dorsal,posterior, and right lateral views of pygidium, locality 3069-2, X 7i-39, 44, Left lateral and ventral views of hypostome, locality 3069-2,X 3- 40, 41, 42, Exterior, posterior, and interior views of paratyperostrum, U.S.N.M. No. Ii65i4d, locality 3070-2, X 6. 45, Dorsalview of free cheek, locality 3069-4, X 3- Helms formation, ChesterSeries, upper Mississippian, Hueco Mountains, west Tex. Localitynumbers are explained on page 1.PLATE 3Paladin {Paladin) helmsensis Whittington, new species 71, 2, Exterior and interior views of incomplete cranidium, showingthe four pairs of glabellar furrows and the pits in the external sur-face, locality 3070-4, X 6. 3, Anterior view of broken edge of freecheek, showing thickness of exoskeleton, locality 3070-4, X 6. 4, 6,Exterior and interior views of paratype free cheek, U.S.N.M. No.116514a, showing eye surface and Panderian notch (p), locality3070-2, X 7i- 5, Interior view of incomplete pygidium, showingmuscle scars as dark patches between ring furrows of axis, andthickness of exoskeleton, locality 3070-2, X 6. 7, 8, 9, Posterior,dorsal, and left lateral views of paratype segment, U.S.N.M. No.116514c, locality 3070-4, X 3- 10, 11, 12, Ventral, posterior, and an-terior views of paratype segment, U.S.N.M. No. Ii65i4g, locality3069-4, X 6. rp = ring process ; ap = axial process ; as = axialsocket ; g= groove in posterior edge of inner part of pleura. 13,Dorsal view of same, X 3- 14, Interior view of paratype incompletesegment, U.S.N.M. No. 1 16514b, locality 3069-4, X 7 2, showingnotch in doublure termed Panderian opening. 15, Dorsal view ofparatype segment, U.S.N.M., No. 116514^ locality 3070-4, X 6. 16,Left lateral view of same, X 3- 17, Interior view of right half ofholotype cranidium, U.S.N.M. No. 116513, showing pit in bossformed by anterior pit in external surface, locality 3070-2, X 7i-Helms formation, Chester Series, upper Mississippian, Hueco Moun-tains, west Tex. Locality numbers are explained on page 1.
PLATES

SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122. NO. 10. PL. 1
Paladin (Paladin) morrowensis and Paladin (Kaskia) rarus(see explanation of plates at end of text.)
SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122. NO. 10. PL .
PALADIN (PALADIN) HELMSENSIS(SEE EXPLANATION OF PLATES AT END OF TEXT.)
ITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122. NO. 10. PL. 3
PALADIN (PALADIN) HELMSENSIS(SEE EXPLANATION OF PLATES AT END OF TEXT.)