THE GRAPSOID CKABS OF AMERICA. 363 



Gccarcoidca Milne Edwards, Hist. Nat. Crust., vol. 2, 1837, p. 25; type, 



,0. lalandii Milne Edwards. 

 Pelocarcinus Milne Edwards, Ann. Scl. Nat., Zool., ser, 3, vol. 20, 1853, 



p. 203 [169] ; type, G. lalandii Milne Edwards. 

 Hylueocarcinus Wood-Mason, Ann. Mag. Nat. Hist., ser. 4, vol. 14, 1874, 



p. 189; type, H. hiitnei Wood-Mason. 

 Limnocarcinus de Man, Notes Leyden Mus., vol. 1, 1879, p. G5 ; type, L. 



intermedins de Man. 



Carapace transversely oval, somewhat depressed, with the lateral 

 borders tumid and strongly arched owing to the vault-like expansion 

 of the gill-chambers ; the gastric region particularly well defined. 



The extent of the fronto-orbital border is less than half the great- 

 est breadth of the carapace, that of the strongly deflexed and nearly 

 straight front is from one-sixth to one-seventh the greatest breadth 

 of the carapace. 



Orbits deep, broadly oval, demarcated dorsally by a sharpish, 

 slightly raised border, their outer angle not defined, a wide gap in 

 their lower border; at the inner angle there is a strong tooth which 

 may or may not meet the front ; if it does so, the antennae, which are 

 much reduced in size, are excluded from the orbit. 



The antennules fold obliquely beneath the front, and the inter- 

 antennular septum is of moderate width. 



Epistome sunken, hairy posteriorly so as to appear ill defined from 

 the palate. Buccal cavern rounded anteriorly, not nearly closed 

 by the external maxillipeds, which leave between them a wide rhom- 

 boidal gap in which the mandibles are exposed. 



The external maxillipeds are rather short; their merus lies ob- 

 liquely, and its anterior edge is excavated for the insertion of the 

 palp, which is short and coarse and is completely exposed; their 

 exognath is very short and almost entirely concealed and is without 

 a flagellum. The exognaths of the other maxillipeds are heavily 

 fringed with hair. 



Chelipeds much more massive than the legs, equal or nearly so in 

 both sexes, though larger and longer in the male than in the female. 



Legs stout; in all, the anterior border of the carpus and all the 

 borders of the propodite and dactylus are spiny, there being 6 rows of 

 spines on the dactylus. 



The abdomen in both sexes consists of 7 separate segments and in 

 the male its base covers all the breiidth of the sternum between the 

 last pair of legs. 



The gill-chamber and its lining membrane, and the number of 

 branchiae, are as in C ardisowa. 



Only one species known, recorded from Brazil ( ?) ; Andaman? and 

 Nicobars, Christmas Island, Celebes, Philippines, New Guinea, Loy- 

 alty Islands. 



