332 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 21 



united with front margin of carapace. Ischium of outer maxillipeds in- 

 wardly strongly advanced ; merus subtriangular, dilated outwardly ; a 

 very shallow sinus at articulation of palpus. 



Chelipeds with palm compressed, sometimes carinated ; fingers gaping 

 at base in the male. Ambulatory legs of moderate length, decreasing 

 rapidly in size from the first to last, either cristate or nodose; dactyli 

 unarmed. (Rathbun, 1901) 



Abdomen with seven free segments in both sexes. 



Range: From Santa Maria Bay, west coast of Lower California, and 

 Puerto Refugio, Angel de la Guarda Island, Gulf of California, Mexico, 

 to Santa Elena Bay, Ecuador; Revilla Gigedo Islands; Galapagos 

 Islands. Western Atlantic from Bahama Banks to Cape Frio, Brazil. 

 Mediterranean. Shore to 50 fathoms ; possibly to 70 fathoms. 



Key to the Pacific American Species of Lissa 



la. Branchial ridges compressed; posterior margin biconcave. Carpi 

 of walking legs single crested. Tip of male first pleopod trian- 

 gular, gonopore centered aurivilliusi 



lb. Branchial ridges bilobate; posterior margin sinuous. Carpi of 

 walking legs double crested. Tip of male first pleopod lobate, 

 gonopore eccentric tuberosa 



Lissa tuberosa Rathbun 

 Plate T, Fig. 7; Plate 33, Fig. 3 



Lissa tuberosa Rathbun, 1898, p. 574, pi. 41, fig. 3; 1925, p. 333, pi. 

 246, fig. 1, text-fig. 107. Crane, 1937, p. 59. Garth, 1948, p. 28. 



Type: Male holotype, U.S.N.M. No. 21574, length 16.9 mm, width 

 15.8 mm. 



Type locality: Southern part of the Gulf of California, Mexico, 8 

 fathoms, Albatross station 2824. 



Localities subsequently reported, with collectors: Mexico: Southern 

 part of the Gulf of California, 7-10 fathoms, Albatross (Rathbun* 

 1898) ; Gorda Banks, 20-30 fathoms, Zaca (Crane). Colombia: Utria 

 Bay [Port Utria], 8 feet, from coral, Askoy (Garth). 



Atlantic analogue: Lissa brasiliensis Rathbun. 



Diagnosis: An inflated branchial ridge divided into two lobes between 

 gastric prominence and lateral angle. Posterior margin sinuous, median 

 projection rounded. First three pairs of ambulatory legs with double- 

 crested carpi. Male first pleopod terminating in a sharply bent lobe, the 

 spermiducal opening eccentrically located therein. 



