DESCRIPTION OF A NEW PARASITIC ISOPOD FROM THEHAWAIIAN ISLANDS.
By Harriet Richardson,Collaborator, Division of Marine Invertebrates, U.S. National Museum.
The isopod, which is heroin described, was collected by the U. S.Bureau of Fisheries steamer Albatross among the Hawaiian Islandsin 1902. This species was not included in my earlier report, becauseadditional material was sent in after that report was published.SCYRACEPON HAWAIIENSIS, new species.Body of adult female oval in outline, somewhat asymmetrical.Color uniformly light yellow.Head very large, bilobed, and provided with a wide marginalborder on the anterior half. Eyes wanting. Both pairs of antennae
FlG. 1.?SCYRACEPON HAWAIIENSIS, FEMALE, a, DORSAL VIEW. I), VENTRAL VIEW. (', LATERAL VIEWOF THORAX.
small and inconspicuous; first pair composed of two joints; secondpair composed of four joints. Maxillipeds very large with theexo-podite produced at the inner distal extremity into a long lamella-like process with many smaller lamellae along its inner margin.The lamella-like process of one side overlaps that of the other maxil-
aBull. U. S. Fish Commission, vol. ?_':!, pi. 3, L906, pp. 819-826.
Proceedings U. S. National Museum, Vol. 38?No. 1770. 645
646 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 38.
Fig. 2.?Scyracepon HA
"WAIIENSIS. MAXILLIPED.
liped on the ventral side of the frontal border of the head; theendopodite is triangular.All seven thoracic segments are distinct andsubequal in length. There is a tendency in
all except the first (most marked in the lastfour) to be produced into a dorsal medianboss. This boss is most conspicuous in theseventh segment and takes the form of astrong hook-shaped prominence. The epimeraof the first four segments are conspicuous onthe anterior portion of the lateral margins.Ovarian bosses are present on the first foursegments. The lateral margins of the last threesegments are concealed by the overlappingelongated, anteriorly directed "lames pleu-rales" of the abdominal segments.The six abdominal segments are distinctly separated on the dor-sal side. Each of the first five segments isprovided on either side with two elongate,fringed appendages and a small sac-like bodyon the ventral side at the base of the in-ferior appendage. The superior elongate ap-pendage on either side of each segment is the
"lame pleurale" of the segment, and thesedecrease in size from the first to the fifthsegment, the first being extremely long, thefifth quite small. The inferior elongatedblanches are the outer branches of the ple-opoda and resemble the
"lames pleurales." Theyalso decrease in size fromthe first to the fifth seg-ments. The inner branchesof the pleopoda are five pairs of small sac-likebodies, a pair for each segment on the ventralside of the body, inconspicuous, forming twoconverging longitudinal rows.The uropoda are a pair of elongated append-ages attached to the sixth abdominal segmentand resembling the "lames pleurales" and theouter branches of the pleopoda.There are seven pairs of small, feeble, pre-hensile legs. There are five pairs of incuba-tory plates which overlap in the middle of theventral side, completely inclosing the incubatory pouch. The distalsegment of the first pair is somewhat produced at the inner posterior
Fig. :i. ?Scyracepon iiawaii-knsis. Mandible.
Fig. 4.?Scvracepon ha-WXHENSIS. First la-mella of MARsri'iiM.
no. 1770. 1 MEW //Iirt//.1Y I80P0D?RICHARDSON. 647
angle and has the posterior margin drawn out in small lamellae. Thelast pair is tuberculate at the base.The male has all the segments of the thorax defined and distinctlyseparate. Each is provided with a median ventral boss. The head issmall and rounded and provided with eves. The firslpair of antennae are composed of two articles; thesecond pair are composed of four articles. The seg-ments of the abdomen are fused in the middle of thedorsal surface, but are indicatedlaterally by five incisions on eitherside, the last incision being veryslight. The pleopods and uropodsare rudimentary.Two specimens, a male and afemale, were collected by the U. S.Bureau of Fisheries steamer Alha-tross, at station 3884, Pailolo Chan-
nel, between Maui and Molokai islands, Territory ofHawaii, at a depth of 277 to 284 fathoms in globige-rina ooze. They were parasitic on Pilumnoplax cocikiRathbun, having been found in the branchial cavity.Type.?Cat, No. 40897, U.S.N.M.Only one species of the genus has been previously described, thetype, Scyracepon tuberculosa Tattersall,tt parasitic on Scyramathiacarpenteri Norman, and found at Tearaght, County Kerry, Ireland.
Fig. 5.?Scyracepon ha-waiienni.s. Second legof female.
Fig. ?.. Scyrace-pon IIAW.UIEN'SIS.Male.
a Fisheries, Ireland, Sci. Invest., L904, vol. 2 [1905], pp. :},(>-M , pi. 11, figs. 9-12;p. 78.