148 University of California Publications in Zoology (Vou. 23 
2. Ambulatory legs considerably longer than greatest width of carapace, 
often about twice or nearly twice as long. 
a. Abdomen well calcified, median row of plates of segments three to 
five replaced by a membranous area well armored with 
numerous spiny, calcified nodules. Carapace more or less 
strongly spined, not less than four sharp-pointed spines on 
gastric region. 
i. Plates of basal (second) abdominal segment distinct, sep- 
arated by sutures. (Known only from 155 + fathoms.) 
Paralithodes, p. 160. 
ii. Plates of basal (second) abdominal segment more or less 
fused, either completely so, or with median and lateral 
or lateral and marginal plates fused together. (Known 
only from 301+ fathoms.) 
Lithodes, p. 161. 
b. Abdomen more or less leathery, median row of plates of seg- 
ments three to five distinct and separate; basal (second) 
segment entire. Upper surface of carapace more or less 
tuberculated or covered with numerous short, blunt spines, only 
one sharp spine on gastric region. (Known only from 625 + 
fathoms. ) 
Paralomis, p. 158. 
The genera of this family are for convenience divided into two groups, based 
primarily on the character of the abdomen, corresponding to the major divisions 
of the above key (Brandt, 1850, p. 259; Bouvier, 1896a, p. 16). The apparent 
basal segment of the abdomen is in reality the second, while the last, or terminal 
(ultimate) segment, or plate represents the telson. 
I. Abdomen soft, more or less loosely inflexed, unsegmented; at most only basal 
(second) and two terminal segments, stiffened by thin calcareous plates ; 
reinforcement of basal segment usually consisting of a pair of narrow 
marginal plates and a pair of lateral plates, between which there may be 
a median plate; abdomen occasionally armed with calcified granules or short 
spines. Carapace more or less distinctly flattened, occasionally slightly but 
never strongly convex, lyrate or roughly quadrilateral; front moderately 
broad; rostrum scarcely if at all exceeding the eye-stalks. (Group II, 
p. 153.) 
Genus Hapalogaster Brandt 
Carapace, chelipeds, and ambulatory legs much flattened and more or less 
hairy or pubescent; lateral margins of carapace with a few small teeth or spines. 
Basal (second) abdominal segment with a thin, transverse, calcareous lateral plate 
on either side; a pair of marginal plates present but small and inconspicuous. 
KEY TO THE CALIFORNIA SPECIES OF HAPALOGASTER 
I. Hand of larger cheliped densely covered with short hair, somewhat roughened or 
granulated at the insertions of the hair, not spinous or tuberculated except 
for one or more small caleareous tubercles on inner face, behind articulation 
of the dactyl. Lateral margins of carapace with not more than two small 
teeth on each side. (From Cape Mendocino to Monterey.) 
cavicauda, p. 149. 
