322 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.21 



Genus LIBINIA Leach 



Libinia Leach, 1815a, p. 129. Milne Edwards, 1834, p. 298. Rathbun, 

 1892, p. 235 (part: not L. macdonaldi or L. spinimana) ; 1925, p. 

 310. 



Type: The Atlantic Libinia emarginata Leach, 1815, by monotypy. 



Description: Carapace convex; tuberculous or spinous; triangular- 

 orbiculate and evenly rounded behind the frontal region. Preocular spine 

 usually distinct. Rostrum emarginate or bifid at the apex. Orbits small, 

 nearly circular, with a superior fissure closed or nearly so, and a closed 

 fissure or an open sinus below. Basal antennal segment moderately en- 

 larged. Merus of external maxillipeds truncate at distal end. Chelipeds 

 well developed ; palm elongate ; fingers evenly denticulate on inner mar- 

 gins. Ambulatory legs well developed, sometimes elongate, diminishing 

 in length from first to fourth pair; segments subcylindrical, usually un- 

 armed. (Rathbun, 1925) 



Abdomen composed of seven articles in the two sexes. (Milne Ed- 

 wards) 



Range: Pacific Ocean from Playa Maria Bay to Magdalena Bay, 

 Lower California, and from near mouth of Colorado River to San 

 Ignacio Bay, Gulf of California, Mexico; vicinity of Paita, Peru. Shore 

 to 51 fathoms. Atlantic Ocean from Windsor, Nova Scotia, to Gulf of 

 San Matias, Patagonia; questionably from Bermuda; Gaboon, West 

 Africa. In the Atlantic to 68 fathoms. 



Key to the Pacific American Species of Libinia 



la. Rostral horns strongly divergent. Two large teeth on basal an- 

 tennal article. Lateral margin strongly rimmed. Merus of cheli- 

 ped armed with spines and tubercles. Male first pleopod stout, 

 keel not equally advanced with tip. Southern Hemisphere 

 rostrata 



lb. Rostral horns not divergent. Only one tooth on basal antennal 

 article. Lateral margin not strongly rimmed. Merus of cheliped 

 unarmed. Male first pleopod slender, keel equally advanced with 

 tip in old specimens. Northern Hemisphere 

 2a. Rostrum short, ascending. Median spines 8 ; hepatic spines 

 2. Tip of male abdomen triangular .... setosa 

 2b. Rostrum longer, horizontal. Median spines 6; one hepatic 

 spine. Tip of male abdomen rounded . . . mexicana 



