182 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 21 



Pleopod 1 medium stout, apex most varying (hammer-shaped ; divided 

 into 3-4 lobes; etc.). Pleopod 2 short. (Stephensen) 



Key to the American Genera of the Subfamily 



Acanthonychinae (after Balss) 



(Pacific genera are shown in bold-face type and are treated in this work) 



(Intercalated spine absent in entire group) 



la. Rostrum double 



2a. Seven free abdominal segments in both sexes 



3a. Antennae visible at sides of rostrum in dorsal view 

 4a. Postorbital tooth lacking. Rostrum bifurcate for 

 half its length, horns widely divergent 



Menaethiops 



4b. Postorbital tooth present. Carapace with two 

 lateral expansions, one hepatic, one branchial 

 5a. Lateral expansions both very broad, leaflike 

 branchial overlapping hepatic dorsally 



Mimulus 



5b. Lateral expansions narrower, inwardly sepa- 

 rated Pugettia 



3b. Antennae not visible at sides of rostrum in dorsal view 

 6a. Carapace broadly oval. Postorbital tooth small or 



lacking Taliepus 



6b. Carapace subtriangular or subpentagonal. Postor- 

 bital tooth of normal size 



7a. Rostrum long, composed of two contiguous 

 spines. Legs not cristate . Sphenocarcinus 

 7b. Rostrum short, composed of two closely ap- 

 proximated horns with arcuate margins. Legs 



cristate Leucippa 



2b. Six free abdominal segments in both sexes. Legs subchelate 



Acanthonyx 



lb. Rostrum single, or secondarily divaricate 



8a. Six free abdominal segments in male, five in female 



Epialtus 



8b. Five free abdominal segments in male 



9a. Five free abdominal segments in female 



10a. Eyestalks short, immovable. Carapace nodose 



Mocosoa 



