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

CEUSTACEA. 255exists on the fifth segment ; the terminal segment is much narrowerthan the preceding, acute and constricted at base. The eyes areplaced in very small orbits ; the antennules lie in oblique fossettes ;the bases of the antennas are almost completely fused with the surroundingparts of the carapace (in the single specimen examined),and scarcely any trace remains of a flagellum. The merus-joint ofthe outer maxillipedes is triangulate, and shorter than the preceding ;the exognath has its outer margin straight, and, although robust, isnarrower than the ischium of the endognath, it does not reach tothe extremity of the merus-joint. The chelipedes are subequal andof moderate length, with the joints granulated, but otherwise unarmed; merus trigonous ; carpus very short ;palm externally ratherconvex, with an angulated prominence on its inner surface, shorterthan the fingers, which externally are longitudinally sulcated, meetalong their inner margins when closed (these margins being minutelydenticulated), and are concave internally toward and somewhatincurved at the tips. The ambulatory legs (which are partiallyconcealed beneath the carapace) have all the joints strongly granulated; the dactyle slender, and longer than the preceding joints.The colour (in spirit) of the single specimen is nearly white. Lengthnot quite 3 lines (6 millim.), breadth nearly 4 lines (8 millim.).The single specimen was collected at Port Molle, 5-12 fms.(No. 118), and is a male, the first, I believe, recorded of this genus.The very prominent front seems to distinguish this species fromall hitherto recorded, except Oreopliorus jp^tneus*, from NewCaledonia, which is only distinguished by the much shorter,more dilated immobile fingers of the chelipedes, and by having thelateral margins of the carapace marked by three closed fissures,whereas in 0. frontalis there are but two, which meet behind andcircumscribe the hepatic region. There are two specimens thatprobably belong to 0. petneus in the collection of the Museum, froniShark Bay, W. Australia {F. M. Ecn/ner, H.M.S. Herald ' '). Theseforms are certainly intermediate between Oreophorus and Tlos, butseem to me to have more affinity with the former gejius, since inTlos muriger, Ad. & White (the typical species), the front is not atall prominent, and its margin, with the antero-lateral margins ofthe carapace, is dorsally reflexed.In the elongated fingers it resembles 0. rugosus, Stimpson, asfigured by A. Milne-Edwards t, from the Loochoo Islands and CochinChina, which, however, has a much less prominent front and thecarapace more coarsely punctulated, and is without the hepaticsulcus. Mr. Haswell (Cat. p. 130) records 0. ru'gosus from PortDenison ; but as his description is merely abbreviated from that ofMilne-Edwards, I am unable to say Avhether the specimens there"coUected afford any basis for uniting 0. rngosus and 0. frontalis.* Tlos petrceus, A. M.-Edwards, ISouv. Arcli. Mus. Hist. Nat. x. p. 51, pi. iii.fig. 1 (1874).t Ann. Soc. Entom. France, ser. 4, r. p. lo2, pi. ti. fig. 3 (1865).