CALIFORNIA STALK-EYED CRUSTACEA. 31 



These crabs are generally found so thickly covered 

 with foreign growths, such as hydroids, seaweeds, bryo- 

 zoans and sponges, that, in their natural environment, 

 they are scarcely recognizable as crabs at all. 



Family MAIID^. 



"Ej'es retractile within tolerably well-defined orbits which are often 

 more or less incomplete below, or marked with open fissures in their 

 upper and lower margins. Basal antennal joint always more or less 

 enlarged." 



Subfamily MAIIN^. 



"Carapace usually subtriangular. Kostrnm well-developed. Anterior 

 legs in the male usually enlarged; fingers not excavate at the tips." 



Key to the Gexera. 



Eostrum vertically compressed and notched. Orbits shallow. 



Ambulatory legs compressed and flattened Chionoecetes. 



Ambulatory legs subcyliudrical. 



Second joint of antenna dilated. Carapace lyrate Hyas. 



Second joint of antenna slender, subcj'-lindrical. Carapace 



pyriform , Herhstia. 



Rostrum composed of two more or less divergent spines. Orbits deep. 

 First ambulatory legs very long. Rostral horns slender. 



Carapace spiny Hyastenus. 



First ambulatory legs moderate. 



No preocular spine Pelia. 



A preocular spine. Rostrum flattened Scyra. 



Genus Hyas Leach. 



Rostrum bifid, flattened, the horns hy a narrow fissure. Orbits shallow 

 and open above, with a fissure above and below. Eyes partially visible 

 from above when retracted. No preocular spine. Basal antennal joint 

 much enlarged, the second moderately dilated, the third narrow. Cara- 

 pace flattened, more or less tuberculated, but not spiny. Ambulatory legs 

 subcylindrical and of moderate length. 



Type. — Hyas araneus. 



