194 University of California Publications in Zoology [Vow. 23 
B. Basal joint of antennae usually either extensively produced outward 
or with one or more distal spines. Eyes with orbits. Postocular 
spine cupped, or with dense growth of hair on anterior face so that 
cornea of retracted eye is partially concealed from above. Exognath 
of outer maxillipeds widest in basal half, tapering gradually. Ros- 
trum bifid. 
1. No preocular spine. 
a. Carapace but slightly longer than wide; surface uneven, tubercu- 
lated or spiny. Rostrum short, flattened, and notched. 
Chionoecetes, p. 209. 
b. Carapace much longer than wide; surface smooth, devoid of 
spines. Rostrum composed of two narrow, divergent spines, 
united basally, for half their length. (Not known north of 
San Pedro.) 
Pelia, p. 210. 
2. A preocular spine. 
a. Postocular spine flattened and densely hairy on anterior face. 
Carapace with numerous or very prominent tubercles or spines. 
Rostrum bifid. (Not known north of Point Reyes.) 
Loxorhynchus, p. 212. 
b. Postocular spine deeply cupped on anterior face and without 
hairs. 
i, Rostrum composed of two long, slender, straight, cylindrical 
spines, diverging from the base. Carapace pyriform, in- 
flated, and covered with sharp spines of unequal length. 
Chorilia, p. 208. 
ii. Rostrum composed of two short, flattened horns. 
a. Rostral horns extremely flattened and leaf-like, about one- 
quarter length of carapace. Orbits deep. Outer mar- 
gin of basal antennal joint flattened and produced, not 
spiny. Carapace subpyriform, furnished with rounded 
tubercles. 
Scyra, p. 213. 
b. Rostral horns very short, one-ninth to one-tenth length of 
carapace. Orbits shallow. Outer margin of basal 
antennal joint not produced, spiny. Carapace sub- 
orbicular, tubereulated. (Not known north of Mon- 
terey Bay.) 
Herbstia, p. 215. 
As can be seen from a review of the above key, the genera of the Inachidae 
arrange themselves into two major groups, based on the proportions of the basal 
antennal joints. In order to facilitate the presentation of generic definitions, 
they are so grouped below: 
I. Basal joint of antennae extremely slender throughout its length and usually 
long; length measured from raised margin of endostome to insertion of 
free joints greater than or at least equal to the combined width of the 
joints and that portion of the epistome or antennular fossettes lying be- 
tween them, measured from bases of eye-stalks (middle of lower orbital 
margin). (Group II, p. 200.) 
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