THE CANCROID CRABS OF AMERICA 455 



Description. — Carapace convex, smooth posteriorly, and with a 

 transverse ridge, interrupted at the middle, on the protogastric, epi- 

 gastric, and frontal regions, and one on each hepatic and epibranchial 

 region. Front convex, strongly projecting, the two lobes triangular, 

 separated by a large V-shaped sinus from which arises a deep furrow 

 extending backward to the gastric region; each lobe with tip rounded, 

 outer margin very oblique, concave, outer tooth small, separated from 

 orbital tooth by a very obtuse angle. Superior orbital sinuses not 

 far apart. The normal second tooth of the lateral margin is com- 

 pletely absorbed in the first or orbital tooth. This and the other 

 three teeth are strong, the last two with a median ridge, the last (or 

 true fifth) tooth larger than common in Micropanope. Outer hiatus 

 of orbit almost obsolete; inferior inner tooth of orbit prominent, sub- 

 conical, tip narrow, subacute. 



Chelipeds large, smooth, polished; carpus with a broad depressed 

 tooth at inner angle, and a short crest, bordering a depressed area, at 

 outer angle; hands short, broad and compressed above, where a smooth 

 crest is formed; posterior outer extremity of hand protuberant and 

 more or less bituberculate. Fingers black with white tips; those of 

 the smaller chela much deflexed and longer than the palm; color of 

 immovable fingers extended on palm. Ambulatory legs rather com- 

 pressed and faintly crested above; dactyli pubescent. 



Measurements. — Male type, length of carapace 5.6 mm. (.22 inch), 

 width of same 6.9 mm. (.27 inch). Male (46080), total length of 

 carapace 5.3 mm., width of same 7, fronto-orbital width 4.6, width 

 of front 2.4 mm. 



Range. — West coast of Mexico. 



Material examined. — Manzanillo, State of Colima; on drifted pile; 

 July 17, 1913; C. R.Orcutt; 1 male, 2 females (1 ovigerous) (46080). 



Genus RHITHROPANOPEUS Rathbun 



Rhithro'panopeus Rathbun, Bull. Labor. Nat. Hist. State Univ. Iowa, vol. 4, 1898, 

 p. 273; type, R. harrisii (Gould). 



Allied to Panopeus. Carapace subquadrilateral, approaching the 

 Goneplacidae in form, dorsal ridges prominent, postero-lateral mar- 

 gins not markedly convergent. Front less than a third as wide as 

 carapace, horizontal, margin thick, double-edged. Upper emargi- 

 nations of orbit obsolescent. Eyes filling, orbits. Chelipeds very 

 unequal, heavy; major dactylus without large basal tooth. Third or 

 coalesced segment of male abdomen not reaching coxae of last pair 

 of legs. 



Contains only one species. 



