THE GKAPSOID CRABS OF AMERICA. 285 



Antennules transverse, fossae narrow ; septum transverse. Antero- 

 €xternal angle of second joint of antennal peduncle a good deal pro- 

 duced ; flagellum slender and rather short, lying in the orbital hiatus. 



Epistome well defined, prominent, rather short fore and aft. 

 Buccal cavern nearly square. The external maxillipeds leave be- 

 tween them a large rhomboidal gap, which is a good deal filled up 

 by a hairy fringe; they are obliquely traversed, from a point behind 

 the antero-external angle of the ischium to the antero-internal angle 

 of the merus, by a conspicuous line of hairs; the coarse palp is 

 attached to the rounded summit of the obliquely directed merus. 



Chelipeds massive in the male, subequal; palm high and short; 

 fingers subacute and hollowed at tip. 



Legs differing little in length, third pair longest; meropodites thin. 



Abdomen in both sexes with seven separate segments, in the male 

 occupying the whole breadth of the sternum between the bases of the 

 last pair of legs. In the female the last segment is small and more or 

 less impacted in the broad sixth segment. 



Distribution. — Tropical and subtropical seas; often distant from 

 the shore. 



KEY TO THE AMERICAN SDBGENEUA AND SPECIES OF THE GENUS SESAttMA. 



A\ Carapace with a lateral tooth behind the outer orbital tooth. 

 B\ Manus with oblique, coarsely pectinated ridges on upper surface. 



Subgenus Chiromantes, p. 287 ; africanum, p. 287. 

 B^ Manus without oblique, pectinated ridges on upper surface. 



Subgenus Sesarma, p. 288. 

 C\ Sides converging anteriorly. Legs narrow and very long. 



verleyi, p. 288. 

 C'. Manus with a definite marginal line above. 

 D\ Front more than half as wide as carapace. 

 E*. Carapace deeply grooved. 



F'. Lateral margins nearly stx'aight, curving In at the orbital tooth. 

 About 11 strong blunt spinules on upper surface of movable 



finger sulcatum, p. 289. 



F*. Lateral margins sinuous. About seven to nine depressed spiui- 

 form tubercles on upper surface of movable finger. 



reticulatum, p. 290. 

 E*. Carapace slightly grooved. 



F\ Spines on upper surface of movable finger extending its entire 



length and about eight in number aeguatoriale, p. 292. 



F*. Spines on upper surface of movable finger restricted to basal half 

 or three-fifths. 

 G\ Carapace four-fifths or less than four-fifths as long as wide. 

 H\ Width of male abdomen gradually diminishing from third to 

 sixth segment. Granules on upper edge of movable finger 



continued a little on distal half curacaocnse, p. 293. 



H*. Male abdomen wider at third segment, abruptly contracted at 

 fourth segment. Granules on upper edge of movable finger 



not continued on distal half rhisophorae, p. 294. 



G*. Carapace more than four-fifths as long as wide. 



crassipes, p. 294. 



