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

—;CRUSTACEA. 273Dana's description of his P. hiunguiculutus *, iu having a distinctlytrilobate front, the middle lobe of which is broad, subacute, orrounded, and not much more prominent than the lateral lobeswhereas in P. biuiu/uieulatus, to which species specimens from theGulf of Suez (R. MacAndreiv) appear to belong, the median lobe isvery prominent and acute and the lateral lobes obsolete. The specimensreferred to P. hiungtiicidatus also differ from P. obesulus inhaving the outer surface of the palms of the chelipedes much moreclosely punctulated. The cephalothorax is narrowest in the smallestsizedspecimens ; and in the female from Port Denison (which isone of the largest examples I have seen) is much broader than inthe others ; but I cannot regard this character by itself as of specificimportance.I am inclined to doubt whether the genus Polyonyx is distinctfrom Merjahhrachium. Stimpson merely distinguishes the latteron account of the absence of the prominent accessory claw, whichgives to the dactjli of the species of Polyonyx a biunguiculateappearance. The type of MeyaJohrucMum (31, yranuliferum, Stm.)is from the West Indies ; but Stimpson refers the P. macrochelii,Gibbes, from Carolina, to the genus Polyonyx. The other species ofthe latter genus are Oriental in habitat.Specimens are referred to P. hiunguiculatus by Mr. Haswell fromHolborn Island, Port Denison, by whom also this species is retainedin the genus Porcellana (vide Cat. p. 147).17. Pachycheles pulchellus (Haswell). (Plate XXX. fig. A.)Porcellana nulchella, Haswell. Proc. Linn. Sac. N. S. Wales, vi. p. 768(1881) ; Cat. Austr. Crust, p. 148 (1882).As Mr. Haswell's description is very brief, I append the followingfrom specimens received from Dr. Coppinger :The carapace is smooth, rather convex, rounded on the sides, andhence somewhat orbiculate in outline, faintly striated on the sidesat the back of the branchial regions. The front is rather broad, andin a dorsal view its margin appears straight ;in an anterior view itis seen to be bisinuated, with a broadly rounded but verj' slightlyprominent median lobe. The orbital and lateral margins of thecarapace are entire. The first exposed joint of the peduncle of theantennae is shorter than the following joint, and has sometimes asmall blunt prominence on its inner margin ; the third joint isshort; the flagellum somewhat elongated, with the joints almostnaked. The ischium of the outer maxillipedes has a spine at itsouter distal angle ; the next joint has a prominent lobe on itsinner margin ; the three following joints are robust. The chelipedesare robust, but not so broadly dilated as in most species of thisgenus ; the merus or arm is verj' short ; wrist with broad low promiuencesdisposed in longitudinal series on its upper surface, and* Vide U.S. Explor. Exped. xiii., Ci-ust. i. p. 411, pi. xxvi. fig. 1 (1852).X