272 
THE VOYAGE OF H.M.S. CHALLENGER. 
is not deflexed, is less than half the width of the carapace, and is deeply cleft by the 
antennulary fossae ; these fossae, in which the antennules are vertically plicated, are open 
in a dorsal view. 
The orbits are deep, and their interior hiatuses are large and open. The epistoma is 
very short and transverse. The anterior margin of the buccal cavity is cri stated. The 
endostomian ridges are usually distinctly developed. The post-abdomen (in the male) 
is broad and triangulate, and occupies at the base the whole width of the sternum between 
the coxae of the fifth ambulatory legs, and is distinctly seven-jointed. The eye-peduncles 
are very short and robust. The basal joint of the antennae is considerably dilated and is 
slightly produced at its anterior angles ; the antero-internal angle reaches the front, and 
the following joint is articulated in the middle of the distal margin of the basal antennal 
joint. 
The exterior maxillipedes are rather small ; the merus of the endognath is shorter 
than the ischium, but not narrower at the base than that joint, distally truncated, and bears 
the next joint at its summit ; the exognath is slender. Chelipedes (in the male) subequal, 
and moderately developed ; merus trigonous, carpus and palm usually granulated ; palm 
rounded above and not dilated ; fingers distally excavated, with corneous tips. Ambu- 
latory legs large and robust; the merus-joints compressed, and with one or more spines 
on the anterior margin ; dactyli strongly spinuliferous. 
In the nearly allied genus Leiolophus, the merus-joint of the exterior maxillipedes is 
very small ; much narrower at the base than the distal extremity of the ischium, and the 
dorsal surface of the carapace is marked with smooth naked lines or ridges. 
Plagusia depressa (Fabricius). 
Cancer depressus, Fabricius, Entoru. Syst. Suppl., p. 406, 1775. 
Cancer squamosus, Herbst, Naturgesch. der Krabben u. Krebse, vol. i. p. 260, pi. xx. fig. 113, 
bad, 1790. 
Plagusia depressa, Say, Journ. Acad. Nat. Sci. Philad., yoI. i. p. 100, 1815. 
,, ,, Miers. Ann. and Mag. Nat. Hist., ser. 5, vol. i. p. 149, 1878, and references 
to synonyma. 
„ „ de Man, Notes Leyden Mus., vol. v. p. 168, 1883. 
„ tuberculata, Lamarck, Hist. Anim. sans Vert., p. 247, 1818. 
„ „ (var.), Miers, tom. cit., p„ 148, 1878, et synonyma. 
St. Vincent, Cape Verde Islands, July 1873 (an adult male). 
In this specimen the lobes above the bases of the second and third ambulatory legs 
are either not at all or very obscurely dentated. There can be little doubt that the 
Indo-Pacific form ( Plagusia tuberculata, Lamarck), which I, following the late Dr. 
Stimpson, regarded as a distinct species, on material which further research has shown 
