PART 1 GARTH : PACIFIC OXYRHYNCHA 37 



Inachinae Composcioidea Stephensen, 1945, p. 218 [error for Cam- 

 poscioidea Balss]. 



Eyes without orbits; eyestalks generally long, either non-retractile, 

 or retractile against sides of carapace, or against an acute postocular spine 

 affording no concealment. Basal article of antennae extremely slender 

 throughout its extent, and usually long. (Alcock, modified) 



Pleopod 1 not very stout; straight or curved, apically tapering, but 

 apex most varying (hairy, spinose, naked, etc.; acute, blunt, bifid, etc.). 

 Pleopod 2 short. (Stephensen) 



The genus Oregonia has been removed from the Alcockian subfamily 

 because of its rectangular male abdomen and filamentous first pleopod. 



With respect to the subdivisions proposed by Balss (1929), the genus 

 Eurypodius alone among those treated allies itself with the more primitive 

 Macrocheiroidea, while the remaining Pacific American genera find their 

 affinities with the Camposcioidea. 



The sequence of genera reflects a gradual loss or reduction in number 

 of parts: from double to single rostrum; from presence to absence of 

 both the interantennular and supplementary orbital spine ; and from the 

 greater to the lesser number of free abdominal somites. 



Key to the American Genera of the Subfamily Inachinae 



Alcock (based on Balss) 



(Pacific genera are indicated by bold face type and are treated in this 



volume) 

 la. A spine intercalated between pre- and postorbital spines 



(Macrocheiroidea Balss) 



2a. Seven free abdominal segments in both sexes; interanten- 

 nular spine present Eurypodius 



2b. Six free abdominal segments in both sexes . Achaeopsis 

 lb. No spine intercalated between pre- and postorbital spines 



(Camposcioidea Balss) 



3a. Seven free abdominal segments in both sexes ; rostrum double 

 4a. Eyestalks long, slender, exposed from bulbous bases; 

 rostrum short; ambulatory legs of first pair not elong- 

 ated Eucinetops 



4b. Eyestalks short, thick ; rostrum long ; ambulatory legs of 

 first pair greatly elongated . . . Anomalothir 

 3b. Six free abdominal segments in male, five in female 



5a. Rostrum double (except in Collodes tenuirostris) ^c 



o\-> 



