Report on the zoological collections made in the Indo-Pacific Ocean ...

CET7STACEA. 269carpus and penultimate joints alternately banded with yeUow andred.The type of Leach's P. lamarcl'ii (from Australia) in the Museumcollection has lost its chelipedes; hence the identification is notcertain ; but the carapace in all respects agrees with the specimensdescribed above, and there exists a distinct postocular spine on thelateral margins.The type specimens of P. asiatims, from the Mauritius, are oflarger size, but scarcely differ except in having the anterior marginsof the wrists armed with more distant, but relatively smaller teeth,and in having the distal ends of the merus-joints of the first andsecond ambulatory legs more distinctly denticulated. Specimensapparently belonging to this form are in the Miiseum collectionfrom various islands of the Pacific and Malaysian seas ; and I thinkit very probable that it should be united with P. lamarclii. Imay note here that the specimen recently figured by Eichters* asP. asiatims. Leach (and by him retained in the genus Porcellana),has a more distinctly truncated median frontal lobe, and only twoteeth on the posterior margin of the arm of the chelipede, and mayperhaps belong to a distinct species.V3. Petrolisthes liaswelli. (Plate XXIX. fig. A.)Carapace flattened, longer than broad, and marked with fainttransverse strife, which are bordered with short hairs ; the lateralmargins are cristated, the carinee extending from the outer orbitalangles to about the middle of the branchial regions ; the front issubtriangulate, with the apex rounded and concave above, themargins somewhat sinuated : the outer orbital angle is not veryprominent, behind it there is a spine on the hepatic region ; the upperorbital margins are entire. The eyes are short and thick. Thereis a prominent tooth or lobe i;pon the antepenultimate joint of thepeduncle of the antenna}, whose flagella are very long and naked.The chelipedes are moderately robust, the merus or arm very short,with a prominent lobe at the distal end of its inner margin : thecarpus is flattened above, its upper surface tuberculated, the tubercles,which in the middle line are generally larger, are flattened andbordered with short hairs ; its anterior margin armed with four orfive unequal teeth, whose margins are themselves generally denticulated; the posterior margin armed with three spines at its distalend ;palm and fingers closely tuberculated on their outer surface,the tiibercles bordered with short hairs, and merging toward theupper margin into longitudinal striae ; the lower margin of thepalm is straight and subcristated ;fingers shorter than the palm,meeting along their inner edges, and incurved at the tips. Ambulatorylegs slightly hairy, with the merus-joint moderately dilatedand compressed, without spinules or teeth, except one or two smalldenticles at the distal end of the lower margin ; the following joints* In Mobius, Beitr. ziir Meeresfauna der Insel Mauritius &c., Decapoda,p. 159. pi. xvii. fig. 13 (1880).