74 CALIFORNIA ACADEMY OF SCIENCES, 



Subtribe CATOMETOPA, or GRAPSOIDEA. 



Carapace wide in front, often subquadrate, sometimes subglobose, and 

 truncated or arcuated anteriorly but not rostrate. The front is usually 

 wide and bent downward. Epistome short, often almost linear. The 

 palp of the maxillipeds may be articulated at the apex or at the inner or 

 outer angle of the merus. Branchise generally less than nine; efferent 

 branchial channels as in the Maioidea. Verges in the male in the coxas, 

 sternum, or in the coxae of the last pair of legs, thence passing through 

 channel in the sternum beneath the pleon. 



This group contains four families, the Gecarcinidse, 

 Ocypodidse, Grapsidse and Pinnotheridse. The first 

 family, the Gecarcinidae, includes land crabs and is not 

 represented by any species within our limits, although 

 there are several in Lower California and Mexico. 



Family OCYPODID^. 



Carapace moderately convex, cancroid or trapezoidal in form, with the 

 antero-lateral margins straight or rounded, and the branchial regions not 

 greatly dilated. Front of moderate width or very narrow. Orbits and 

 eye-stalks of moderate size or greatly developed. Palp of external maxil- 

 lipeds joined to the antero-internal or rarely the antero-external angle of 

 the merus. Dactyls of the ambulatory legs styliform and devoid of 

 spines. The abdomen usually does not cover the whole width of the 

 sternum between the last pair of legs. 



Species mostly small and littoral. 



Genus Uca Leach. 



Carapace transverse, widest in front, the antero-lateral angles acute; 

 dorsal surface smooth and granulated. Orbits large, extending to the 

 lateral angles; eye-stalks long and slender. Merus of the maxillipeds 

 generally transverse, smaller than the ischium, distally truncated, and 

 not emarginate at the antero-internal angle; palp joined to the antero- 

 external angle of the merus. Chelipeds in the male very unequal; hand 

 in the larger cheliped very large, fingers longer than the palm. Smaller 

 cheliped (both chelipeds in the female) feeble. 



