194 BULLETIN 129. UNITED STATES NATIONAL MUSEUM 



E^. Three long, antero-lateral marginal spines besides the orbital spine. 

 Inferior orbital sinus acute. (True of the typical or American 



species) Chorilibinia, p. 309 . 



C^. Supraocular eave not produced anteriorly in a spine. 



D^ Carapace either broader than long or very little longer than broad. 

 Rostrum short. Chelipeds much shorter than ambulatory legs. 

 E'. Rostrum very small, simple. Basal antennal article reaching to 



line of rostrum leurocyclus, p. 230. 



E^. Rostrum longer than in Leurocyclus, bilobed. Basal antennal 



article not reaching to line of rostrum Chionoecetes, p. 232. 



D^. Carapace considerably longer than broad. Rostrum elongate. 

 E'. Carapace smooth. 



F^ Basal article of antennae narrow; peduncle not reaching end of 



rostrum Pelia, p. 275. 



F2. Basal article of antennae broad, nearly as broad as long; pedimcle 



reaching or overreaching end of rostrum Pisoides, p. 284. 



E^. Carapace rough with tubercles or tubercles and spines. Carapace 

 lyrate; rostrum triangular, horns contiguous or nearly so. 



Hyas, p. 2.52. 

 B^. A tooth on orbital margin between supraocular eave and postocular cup. 

 C Rostrum small. Carapace suborbicular or broadly ovate. 



D'. Ambulatory legs with very long propodites and very short dactyls. 

 Ischium of outer maxillipeds much longer than merus. 



Herbstia, p. 293. 



D2. Ambulatory legs with dactyls nearly as Itwig as propodites. Ischium 



of outer maxillipeds scarcely longer than merus (both measured 



on outer margin) Micropisa, p. 303. 



C^. Rostrum of considerable length. Carapace narrower than in C, dis- 

 » tinctly longer than broad. 



D^ Chelipeds filiform, chelae more slender than merus. Legs much 



stouter, spinous Lepteces, p. 292. 



D2. Chelipeds as stout as, or stouter than, ambulatory legs. 



E'. First ambulatory leg long, much longer than the last three. 



F'. Orbit very open; postorbital tooth small. Carapace oval, mostly 



smooth. Antennae concealed by rostrum Chorinus, p. 304. 



F^. Orbit not very open; postorbital tooth of good size. Carapace 

 pyriform, with four spines forming a square on widest portion. 



Antennae visible at sides of rostrum Notolopas, p. 287. 



E2. Ambulatory legs diminishing regularly from first to fourth pair. 

 Carapace rough with numerous spines. 

 F'. Orbit closed below; postorbital tooth broad. Spines of carapace 



short and stout Nibilia, p. 289. 



F^. Orbit very open above and below; postorbital projection a slender 

 spine. Spines of carapace long and slender__Holoplites, p. 307. 

 A^. Supraocular eave in close contact with the postocular process. (In young 

 Lihinia there may be a narrow open slit in superior orbital margin.) 

 B'. Carapace usually subglobose behind the rostrum, spinous; rostrum invo- 

 lute Libinia, p. 310. 



B2. Carapace subtriangular, lumpy; rostrum more or less revolute. Orbit 

 outward-looking. Basal antennal article tapering, not spined. 



Lissa, p. 331. 



