MAMMALS 289 



Key to the American Genera of Phocidae 



El Teeth 34. 



bi Molars with 2 to 4 cusps each i. Phoca. 



bo Molars with i cusp each 2. Halichoeriis. 



as Teeth 30; snout proboscis-like 3. Cystopltora. 



1. Phoca L. Snout narrow and pointed; dentition 3/2, i/i, 4/4, 

 i^'i; forehead convex; incisors conical: cosmopolitan. 



P. vitulina L. Harbor seal. Color yellowish gray, spotted with 

 black; length 1,500 mm.: circumpolar; southward to Lower California 

 and the Carolinas; common on the New England coast; ascending 

 rivers; occasionally in Lake Champlain and Lake Ontario. 



P. hispida Schreber. Ringed seal. Color blackish above, with 

 large whitish spots; length 1,500 mm.; body slender; limbs long: circum- 

 polar; southward to Newfoundland. 



P. grcenlandicaYjXxXQhtn. Harp seal. Color gray, with a black face 

 and a black band across the shoulder and extending along the sides; 

 length 1,500 mm.; body slender; weight 600 to 800 lbs.; circumpolar; 

 southward to Newfoundland and the Magdalen Islands; the basis of 

 the sealing industry in Newfoundland. 



2. Halichoerus Nilsson. Snout broad and short; teeth 34; molars 

 conical, with a single cusp; incisors conical; claws well developed: i 

 species. 



H. grypus (Fabricius). Gray seal. Color gray, with irregular dark 

 spots; length 2,500 mm. ; weight up to 3,600 lbs. ; flippers hairy only along 

 the toes: North Atlantic; southward to Nova Scotia. 



3. Cystophora Nilsson. Snout elongated, forming a short proboscis 

 and capable of inflation in the male; dentition 2/1, i/i, 4/4, i/i; 

 incisors conical; molars and premolars small and separated from one 

 another: i species. 



C. cristata (Erxleben). Hooded seal. Color bluish black, with 

 whitish spots; length 2,400 mm.: North Atlantic; southward occasion- 

 ally to Long Island. 



Order 8. Rodentiia.^ — Rodents. Small or medium-sized mammals 

 with long chisel-like incisor teeth, no canines, and grinders (premolars 

 and molars) which are separated from the incisors by a wide space, the 

 incisors having persistent papillae and growing continuously (Fig. 168); 

 feet mostly pentadactylous and plantigrade; placenta discoidal: 

 about 1,400 species grouped in about 21 families, constituting a third 

 of all species of mammals and occurring on all the continents; about 

 400 species in the United States. 



