1 921 J Schmitt: The Marine Decapod Crustacea of California 269 



Family Grapsidae 



Carapace quadrate, flattened, or moderately convex; lateral margins straight 

 and parallel or slightly arcuate, frequently toothed; front never very narrow, in 

 general decidedly broad; orbits and eye-stalks of moderate size. Antennules 

 folding back transversely or obliquely. Third maxillipeds with more or less of a 

 gape left between them. 



Key to the California Genera of the Grapsidae 



I. Carapace as long as or longer than broad, suborbicular, smooth. Anterior 

 edges of ambulatory legs with a thick, dense fringe of hair. Pelagic 

 crabs, usually found on floating seaweed in the open ocean. 



Planes, p. 272. 

 II. Carapace considerably broader than long. Anterior edges of ambulatory legs 

 if hairy only sparsely so, never with a dense fringe. Littoral crabs 

 found on mud flats or among rocks along shore. 



A. Carapace transversely striated. External maxillipeds with a wide 



rhomboidal gape between them. 



1. Orbits normal, deep, and concave. 



Pachygrapsus, p. 269. 



2. Orbits not normal, with posterior surface bulging outward, convex 



instead of concave. (Only one specimen known, from San Diego.) 



Grapsodius, p. 276. 



B. Carapace more or less smooth. External maxillipeds only moderately 



gaping. 



Hemigrapsus, p. 272. 



Genus Pachygrapsus Randall 



Carapace marked with transverse striae; anterolateral margins entire, or with 

 one or two teeth. Outer maxillipeds with a wide rhomboidal gape between them; 

 merus as broad as or broader than long, distally truncated, and bearing the palp 

 at its summit. Abdomen of male covers the sternum at its base. 



Key to the California Species of Pachygrapsus 



I. Merus of last pair of ambulatory legs with two or three sharply distinct 

 teeth at posterodistal angle. Frontal (inter orbital) margin distinctly sinu- 

 ous in frontal aspect. Lateral margins of carapace converging posteriorly 

 from the lateral tooth. 



transversus, p. 271. 



II. Merus of last pair of ambulatory legs with posterodistal angle inconspicuously 

 denticulate or entire. Frontal (interorbital) margin practically straight in 

 frontal aspect. Lateral margins of carapace strongly arcuate. 



crassipes, p. 270. 



