THE GKAPSOID CRABS OF AMEEICA. 225 



KEY TO THE SUBFAMILIES AND AMEBICAN GENERA OF THE FAMILY GUAPSIDAE. 



A 1 . The antennules fold beneath the front in the ordinary way. 



B 1 . 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 Crapsinae, p. 226. 



D 1 . Front much less than half the greatest breadth of the carapace. 

 E 1 . Merus of external maxillipeds longer than broad. 



F 1 . Fingers with broad, spooned tips Grapsus, p. 226. 



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



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



Lcptograpsus, p. 234. 

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



carapace. 

 E 1 . Posterior surface of orbit concave. 



F 1 . Antennae excluded from the orbit Goniopsis, p. 236. 



F*. Antennae entering the orbit. 



G 1 . Carapace depressed, distinctly striated Pacliygrapsus, 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 is in line with the anterior border of the epistome. 



Subfamily Varuninae, p. 260. 

 D 1 . First segment of male abdomen not entirely covering the sternum 



between the legs of the last pair. 

 E 1 . Antero-lateral margins arcuate. Merus of external maxillipeds as 



broad as long. 

 F 1 . Surface very uneven. Front strongly advanced. Suborbital 



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



F 1 . 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. 



Hemigrnpsus, p. 264. 



E 1 . Lateral margins straight and parallel. Merus of external maxilli- 

 peds longer than broad Tctragrapsus, p. 273. 



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



legs of the last pair. 

 E 1 . Propodus of large cheliped normal. 



F 1 . Carapace subrotund Glyptograpsus, p. 275. 



F*. Carapace squarish Euchirograpsns, p. 281. 



E*. Propodus of large cheliped prolonged proximnlly far beyond its 



articulation with the carpus Platychirograpsus, p. 278. 



B 1 . An oblique hairy ridge on the exposed surface of the external maxilli- 

 peds Subfamily Sesarminac, p. 283. 



C 1 . Antennae lodged in the orbital hiatus. 



D 1 . Epistome not projecting beyond the edge of the front. 

 E 1 . Carapace quadrate or subquadrate. 



F 1 . Carapace convex Scsarma, p. 2S4. 



F*. Carapace flat MctopaiiJian. p. 317. 



E 1 . Anterior half of carapace with arcuate margin, posterior half rec- 

 tangular. 

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