1921] Schmitt: The Marine Decapod Crustacea of California 269 
Family GRapPsIDAE 
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 
aping. 
eapms 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. 
Kry ToO THE CALIFORNIA SPECIES OF PACHYGRAPSUS 
I. Merus of last pair of ambulatory legs with two or three sharply distinct 
teeth at posterodistal angle. Frontal (interorbital) 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. 
