398 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



fourth legs uniramose, second and third legs biramose, the basipods 

 of the latter broadly laminate and fused into a transverse apron 

 reaching nearly across the carapace. Rudiments of a fifth and 

 sometimes a sixth pair of legs on the lateral margins or at the 

 posterior corners of the fused fifth-genital segment. Egg strings 

 often longer than the entire body. 



KEY TO THE SPEX!IES 



1. Carapace distinctly more than half the entire length 2 



Carapace about half the entire length 6 



Carapace distinctly less than half the entire length 8 



2. Abdomen, without the caudal rami, less than half as long as 



genital segment, with parallel sides 3 



Abdomen, without the caudal rami, more than half as long as 



genital segment, w'ith convex sides 4 



3. Genital segment longer than wide ; basal segment of fourth legs 



with a stout plumose seta curtus (p. 399) 



Genital segment as wide as long; basal segment of fourth legs 



without a plumose seta balistae (p. 400) 



4. Abdomen tapei'ed, distal end half as wide as base ; caudal rami 



turned inward, meeting at their tip rufus (p. 401) 



Abdomen as wide at tip as at base, or wider; caudal rami 

 widely separated . 5 



5. Genital segment widest at center, with posterior lobes ; claws on 



first legs bipartite schistonyx (p. 401) 



Genital segment widest near posterior end, without lobes ; claws 



on first legs simple rufimaculatus (p. 402) 



6. Genital segment wider than long ; abdomen 1-segmented ; dorsal 



surface with irregular pigment spots rapax (p. 403) 



Genital segment as long as wide or longer ; no pigment spots 

 on the dorsal surface 7 



7. Abdomen 2-segmented, three times as long as wide ; caudal rami 



three or four times as long as wide chelifer (p. 404) 



Abdomen l-segmented, only one-third longer than wide ; caudal 



rami one-half longer than wide belones (p. 405) 



8. Genital segment widest near posterior end, much longer than 



the abdomen; the latter 2-segniented mutabilis (p. 406) 



Genital segment widest at center and not longer than the ab- 

 domen ; the latter 1- or 2-segmented 9 



9. Genital segment squarely truncated posteriorly without lobes ; 



abdomen always 2-segmented pelamydis (p. 406) 



Genital segment deeply reentrant posteriorly, with broad lobes ; 



abdomen segments more or less fused bonito (p. 407) 



1. Abdomen, without caudal rami, shorter than genital segment 2 



Abdomen, without caudal rami, about as long as genital segment 4 



Abdomen, without caudal rami, longer than genital segment 5 



2. Abdomen 2-segmented ; genital segment nearly twice as long as 



wide, without leg rudiments mutabilis (p. 406) 



Abdomen 1-segmented ; genital segment with leg rudiments 3 



