THE GRAPSOID CRABS OF AMERICA. 225 



KEY TO THE SCBFAMILIES AND AMERICAN GENERA OF THE FAMILY GUAPSIDAE. 



A*. The antennules fold beneath the front in the ordinary way. 



B\ No oblique hairy ridge on the exposed surface of the external maxillipeds. 

 C\ The lower border of the orbit runs downward toward the buccal cavern. 



Subfamily Grapsinae, p. 226. 

 D\ Front much less than half the greatest breadth of the carapace. 

 E\ Merus of external maxillipeds longer than broad. 



F\ Fingers with broad, spooned tips Grapsus,'i). 226. 



F'. Fingers acute, not spooned Gcograpsus, p. 231. 



E". Merus of external maxillipeds not longer than broad. 



Leptograpsus, p. 234. 

 D*. Front more than half, or about half, the greatest breadth of the 

 carapace. 

 E\ Posterior surface of orbit concave. 



F*. Antennae excluded from the orbit Goniopsis, p. 236. 



F'. Antennae entering the orbit. 



G'. Carapace depressed, distinctly striated_-_Pacfti/firrfl;jsM8, p. 240. 



G^ Carapace convex, almost smooth Planes, p. 253. 



E*. Posterior surface of orbit bulging outward Grapsodius, p. 259. 



C*. The lower border of the orbit does not run downward toward the 

 buccal cavern, but is supplemented by a rather distant suborbital 

 crest, which i.s in line with the anterior border of the epistome. 



Subfamily Varuninae, p. 260. 



D\ First segment of male abdomen not entirely covering the sternum 



between the legs of the last pair. 



E\ Antero-lateral margins arcuate. Merus of external maxillipeds as 



broad as long. 



F\ Surface very uneven. Front strongly advanced. Suborbital 



crest not forming a stridulating ridge Cyrtograpsus, p. 260. 



F'. Surface little uneven. Front moderately advanced. Suborbital 

 crest a stridulating ridge which scrapes against a short and 

 usually horny ridge on the distal end of the arm. 



Hemigrapsus, p. 264. 

 El Liiteral margins straight and parallel. Merus of external maxilli- 

 peds longer than broad Tetragrapsus, p. 273. 



D'. First segment of male abdomen covering the sternum between the 

 legs of the last pair. 

 E\ Propodus of large cheliped normal. 



F' Carapace subrotund Glyptograpsus, p. 275. 



F\ Carapace squarish Euchirograpsus, p. 281. 



El Propodus of large cheliped prolonged proximally far beyond its 



articulation with the carpus Platychirograpsus, p. 278. 



B' An oblique hairy ridge on the exposed surface of the external maxilli- 



^^g Subfamily Sesarminae, p. 283. 



C\ Antennae lodged in the orbital hiatus. 



D\ Epistome not projecting beyond the edge of the front. 

 E* Carapace quadrate or subquadrate. 



F\ Carapace convex Sesarma, p. 284. 



F\ Carapace flat Metopattlias, p. 31*. 



El Anterior half of carapace with arcuate margin, posterior half rec- 

 tangular. 

 65863—17 15 



