PART 1 GARTH : PACIFIC OXYRHYNCHA 433 



Chelipeds not specially mobile, usually much longer and heavier 

 than the other legs, and with fingers bent on the hand at an angle toward 

 the side with the fixed finger. Second article of antenna small, short, and 

 not fused with epistome or front. Orbits well made. Hooked hairs almost 

 always wanting. Male openings coxal. Palp of external maxilliped articu- 

 lated at anterointernal angle of merus. (Borradaile) 



The family is divided into two subfamilies, the Parthenopinae and 

 the Eumedioninae. All of the genera represented in American waters 

 belong to the first, which is by far the larger subfamily. 



Subfamily PARTHENOPINAE 



Parthenopinae Miers, 1879c, p. 668. Alcock, 1895, p. 258. Stephensen, 

 1945, p. 219. 



Carapace commonly equilaterally-triangular, sometimes sub-pentago- 

 nal or ovate-pentagonal, and sometimes almost semicircular or semi- 

 elliptical in outline ; cardiac and gastric regions usually deeply marked off 

 from the branchial regions on either side, making the dorsal surface of the 

 carapace trilobed. Chelipeds vastly longer and more massive than the 

 ambulatory legs. Rostrum simple or obscurely trilobed. (Alcock) 



Pleopod 1 varying, more or less stout, apically tapering or not taper- 

 ing. Pleopod 2 usually short and of usual shape, but in Platylambrus 

 carinatus in length equal to pleopod 1. (Stephensen) 



Key to the American Genera and Subgenera of the Family 



Parthenopidae 



(Rathbun, modified, after Alcock) (Pacific genera are shown in 

 bold face type and are treated in this volume.) 

 la. Carapace not laterally expanded 

 2a. Carapace tuberculate or eroded 



3a. Basal antennal article short, not reaching orbital hiatus 



Parthenope 



4a. Chelipeds more than twice as long as carapace 



5a. Carapace ovate-pentagonal, surface little cari- 



nate .... Subgenus Parthenope 



5b. Carapace broadly triangular, sides rounded, 



surface carinate or tuberculate .... 



Subgenus Platylambrus 



4b. Chelipeds less than twice as long as carapace 



Subgenus Pseudolambrus 



