396 CRUSTACEA 



anteriorly; length of carapace 8 cm.; width 6.4 cm.: Greenland to Vir- 

 ginia; Europe; North Pacific; in 5 to 1,000 fathoms. 



3. Pelia Bell. Carapace triangular, and much longer than broad; 

 surface smooth; eye stalk in an orbit but not completely concealed: 2 

 American species. 



P. mutica (Gibbes). Small spider crabs. Claw of male with nearly 

 parallel sides and with edges which meet only at the tip: Cape Cod to 

 Florida and the Gulf of Mexico, from low-water mark to 15 fathoms. 



Division 2. CYCLOMETOPA.* 

 Carapace more or less circular or elliptical in form and usually 

 broader than long, the front forming a regular arch, and without a 

 distinct rostrum; 9 pairs of gills present: 6 families. 

 Key to the families of Cyclometopa here described: 



Oi First antennae folded longitudinally or nearly so 1. Cancridae 



cfa First antennae folded transversely or obliquely. 



6i Last pair of legs not flattened for swimming 2. Pilumnidae 



hi Last pair of legs flattened for swimming 3. Portunidae 



Family 1. CANCEIDAE. 

 Carapace usually broader than long and with very short rostrum 

 or none at all; anterior margin arched and serrate; last pair of legs 

 pointed at the end: about 4 genera. 



Cancer L. Carapace flattened, and more or less elliptical in shape ; 



the outer maxillipeds completely cover 

 the other mouth parts: 11 American 

 (( /^^^S^^'^^^^^^^^ species, 2 on the Atlantic coast. 



C. irroratus Say. Rock crab (Fig. 

 •fe^ '' ^'^i^M^ 630). Anterior margin of carapace 

 .y .- .;•. '''\\;^:£^^y^^<</ with 9 blunt teeth on each side; length 

 5^^^^^^^^r>^ of carapace 7 cm.; breadth 10 cm.; 



color yellowish, thickly spotted with 

 small reddish dots: Labrador to South 

 ^'^- ^^^atZun)?''""'''"' Carolina; common among rocks and 



in the sand, in which it may lie buried, 

 from low water to 300 fathoms ; the commonest crab on the New England 

 coast, where it is occasionally used for food. 



C. borealis Stimpson. The northern or Jonah crab. Similar to the 

 preceding but larger, with a more convex and much rougher carapace; 

 color brick red : Labrador to Connecticut, often common among the rocks 

 in exposed places, not living under the rocks or in the sandy or muddy 

 bays. 



* See "Synopsis of the Cyclometopous or Cancroid Crabs of North America," by 

 Mary J. Rathbun, Am. Nat., Vol. 34, 1900. 



