THE CRUSTACEA OF NEW JERSEY. 439 



Key to the genera. 



a. Carapace broader than long. sESArma 



aa. Carapace long as, or longer, than broad. planES 



Genus SESARMA Say. 



Sesarma Say, Journ. Acad. Nat. Sci. Phila., I, 1817, p. 76. Type Sesarma 



reticulata Say, monotypic. 

 Pachysoma Haan, Faun. Japon. Crust., 1850, p. 2>2)- Type Grapsus bidens 



Haan, first species. 

 Holometopus Milne-Edwards, Ann. Sci. Nat. Zool., (3) XX, 1853, p. 187 



(153). Type Grapsus {Pachysoma) lucmatocJieir Haan, monotypic. 



Carapace depressed, thick subtrapezoidal, broader than long, 

 antero-lateral margins straight or nearly so, entire or imiden- 

 tated, and slightly convergent to posterior margins. Carapace 

 somewhat convex, usually very distinctly plicated over whole of 

 dorsal surface. Front very broad, deflexed, anterior margin 

 straight and slightly sinuated. Orbits small, interior subocular 

 lobe not reaching front, little developed, so that produced antero- 

 external lobe of basal antennal joint usually enters slightly within 

 orbital hiatus. Epistoma very short, almost linear-transverse. 

 Endostome with longitudinal ridges usually (but not always) 

 distinctly developed. Post-abdomen (in male) distinctly seven- 

 jointed, covers whole sternum width at base. Eye-peduncles 

 short, robust. Antennules transversely plicated in short wide 

 fossettes. Antennae with basal joint very short, entering orbit, 

 more or less produced at antero-external angle and flagellum 

 short. Exterior maxillipeds with rhomboidal gape, merus joints 

 longer than broad with rounded apices, and 1)earing next joint 

 medianly or internally. An external piliferous ridge crosses 

 ischium and merus. Chelipeds subequal, moderately developed, 

 with merus joints trigonus and their anterior margins distally 

 dentated, palms somewhat turgid, rounded above and below, and 

 fingers excavated at distal extremity. Ambulatory legs of mod- 

 erate length, merus joints dilated and compressed, anterior mar- 

 gins with subterminal spine, posterior margins with several spines 

 at distal extremity, and rather short dactyli spiniferous. 



Species widely distributed on warm or tropical shores. 



