SYNOPSES OF NORTH-AMERICAN 
INVERTEBRATES. 
VII. THE CYCLOMETOPOUS or CANCROID CRABS OF NORTH 
AMERICA. 
MARY J. RATHBUN. 
In the Cyclometopa the carapace is usually broader than 
long, regularly arched in front, and not rostrate; the epistome 
is short and transverse; the outer maxillipeds have the fifth 
joint articulated at the inner front angle of the fourth; there 
are nine pairs of branchiz, their efferent channels opening at 
the sides of the endostome or palate; and the genital organs 
of the male are inserted at the bases of the last pair of trunk 
legs. 
This tribe contains many well-known crabs, including all 
the large edible species of the United States — the common 
“blue crab," or Callinectes, of our eastern coast, the stone crab 
(Menippe) of the Southern States, and the large Cancer magister, 
or common crab, of the Pacific coast. 
The Cyclometopa, as represented in North America, may 
conveniently be subdivided into three families: first the Can- 
cride, containing the genus Cancer with eleven species, some 
of which attain a large size and which frequent rocky and 
sandy bottoms, and the genera Telmessus and Erimacrus, hairy 
crabs inhabiting Bering Sea and the North Pacific and furnish- 
ing food for fur seals. 
The remainder of the crabs of cancroid shape, that is, trans- 
versely oval or hexagonal and without projecting spines or 
natatory feet, are included in the family Pilumnidz, many of 
Which are small species inhabiting muddy qmd or living under 
Stones or in crevices of rocks or sponges. 
The family Portunidze, or the swimming aie have, with one 
€xception, the last pair of legs developed into a swimming 
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