PART 1 GARTH : PACIFIC OXYRHYNCHA 435 



hiatus occupied by second [article] of antennal peduncle. Antennules 

 folding obliquely. Antennae small, their basal [article], extremely short 

 and not reaching the front, wedged between the antennulary fossa and 

 the large lobe constituting the floor of the orbit. Buccal frame usually 

 quadrangular, sometimes a little narrowed in front, and completely 

 closed by the external maxillipeds. . . . 



Chelipeds usually of immense size and length, out of all proportion 

 to the short slender ambulatory legs; [arm] and hand usually prismatic, 

 with the borders strongly dentate; fingers much shorter than the palm 

 and abruptly curved inward and a little downward. (After Alcock) 



Range: Eastern Pacific from Magdalena Bay, Lower California, and 

 Angel de la Guarda Island, Gulf of California, Mexico, to Lobos de 

 Afuera Island, Peru ; Revilla Gigedo Islands ; Galapagos Islands. 

 Western Atlantic from S of Martha's Vineyard, Massachusetts, to 

 Ubatuba, Sao Paulo, Brazil. Eastern Atlantic, Mediterranean, and 

 Indo-Pacific. 



Key to the Pacific American Subgenera and Species of 

 Parthenope (after Rathbun) 

 la. Chelipeds more than twice as long as carapace 



2a. Carapace ovate-pentagonal, surface little carinate 



( Subgenus Parthenope) 



Tip of rostrum broadly triangular .... hyponca 



2b. Carapace broadly triangular, carinate or tuberculate, with 



more or less rounded sides . (Subgenus Platylambrus) 



3a. Marginal teeth short, blunt, tuberculiform. Three larger 



tubercles on posterior margin, one median 



exilipes 



3b. Marginal teeth elongate, subacute, spiniform. Four larg- 

 er tubercles on posterior margin, those of inner pair on 

 each side of middle .... depressiuscula 

 lb. Chelipeds less than twice as long as carapace 



(Subgenus Pseudolambrus) 

 4a. Chelipeds stout and contorted. Anterolateral margins angled 

 5a. Chelipeds concave above, surface between crests smooth. 

 Angle of deflection of rostrum 90° . . excavata 

 5b. Chelipeds convex above, surface between crests tuber- 

 culate. Angle of deflection of rostrum less than 90° 



stimpsoni 



4b. Chelipeds angular and dentated. Anterolateral margins 

 nearly straight. An overarching tooth protecting base of an- 

 tenna triangula 



