PART 1 GARTH : PACIFIC OXYRHYNCHA 419 



Genus HEMUS A. Milne Edwards 



Hemus A. Milne Edwards, 1875, p. 88. Rathbun, 1901, p. 62; 1925, 

 p. 345. 



Type: The Atlantic Hemus cristulipes A. Milne Edwards, 1875, 

 by monotypy. 



Description: Carapace thick and swollen; longer than broad. Ros- 

 trum small ; no preorbital spines ; orbit incomplete below. The second 

 and third [first and second movable] articles of the external antennae 

 remarkably expanded and flattened, resembling an external maxilliped ; 

 the multiarticular^ flagellum inserted at the external angle of the third 

 [second movable] article. Merus of the external maxillipeds long and 

 little dilated outwards ; exognath very broad in its basilar and middle 

 portion, and narrowing near its extremity. Chelipeds small, fingers 

 slightly gaping, strongly turned inwards near their extremity, but 

 scarcely spoon-shaped. Ambulatory legs short, but very strong; merus 

 decorated with cristiform extensions ; dactyls large, very much curved, 

 but devoid of denticulations below. (A. Milne Edwards, modified) 



Dilated legs fitting together in such a way that with the antennal 

 peduncle and the deflexed rostrum, they form a large cavity underneath 

 the body. (Rathbun, 1925) 



Abdomen seven-segmented in both sexes. 



Range: Eastern Pacific from Puerto Refugio, Angel de la Guarda 

 Island, Gulf of California, Mexico, to Bay of Santa Elena, Ecuador. 

 Western Atlantic from Cape San Bias, Florida, to Curasao, Nether- 

 lands West Indies. Shore to 32 fathoms. 



Key to the Pacific Species of Hemus 



la. Tips of rostrum closely approximated. Cardiac region high, 

 encroaching on branchial and intestinal regions. Two lateral 

 teeth. Meral shields narrow, surfaces convex. Second free an- 

 tennal segment small, oblique. Male first pleopod simple 

 analogus 



lb. Tips of rostrum widely separated. Cardiac region high, but not 

 extending onto branchial and intestinal regions. Three lateral 

 teeth. Meral shields wide, surfaces concave. Second free antennal 

 segment larger, transverse. Male first pleopod doubly flanged. 



finneganae 



