MAMMALS 273 



N. cynocephalus (LeConte). Mexican bat (Fig. 155). Body 

 plumbeous or dusky brown in color; length 79 mm.; tail 30 mm.; 

 forearm 40 mm.; sides of snout with a series of deep wrinkles; half of tail 

 in interfemoral membrane: southern States; common. 



Order 6. Camivora.— The flesh-eaters. Carnivorous, sometimes 

 omnivorous mammals with large projecting canine teeth, cutting pre- 

 molars and tuberculate molars; the last upper premolar and the first 

 lower molar being carnassial (flesh-cutting) teeth (Fig. 139); digits 

 unguiculate and never less than 4: 250 species, 120 in the United States, 

 grouped in 5 families; predatory mammals distributed throughout the 

 world. 



Key to the Families of Camivora 



ai Claws not retractile. 



bi Tail rudimentary; bears i. UrsidcE. 



hi Tan well developed and long. 



Ci Feet digitigrade; hind foot with 4 toes; wolves; foxes. .2. Canidce. 



C2 Feet plantigrade; hind foot with 5 toes; racoons 3. Procyonidce. 



a2 Claws more or less retractUe. 



bi Hind foot with 5 toes; weasels; skunks 4. Mustelidce. 



hi Hind foot with 4 toes; cats 5. Felidce. 



Family i. Ursidae. — Bears. Body of large size, thick and heavy; 

 feet plantigrade; toes 5-5; claws not retractile: in all geographical 

 regions except the Ethiopean and Austrahan; 2 genera, one of which, 

 Thalarctos Gray, includes the Polar bear, T. maritimus (Phipps). 



Ursus L. Head short and broad; snout depressed; dentition t,!^,, 

 I /i, 4/4, 2/3; molars very broad and tuberculate: many species, about 

 3 in the United States, omnivorous, mainly nocturnal animals which 

 hibernate in the winter. The young, from i to 4 in number, are born 

 in midwinter. The brown bears of Alaska and Arctic America, of 

 which many species have been described, are characterized by their 

 great size, U. middendorffi being the largest and heaviest of the 

 Camivora. 



Key to the United States Species of Ursus 



ai Size moderate; length under 1,700 mm. 



bi Color black, sometimes brown U. americanus. 



hi Color brown or yellowish; in Louisiana and Texas U . luteolus. 



a2 Size very large; length over 1,700 mm U. horribilis. 



U. americanus Pallas. Black bear; cinnamon bear. Body black, 

 with a brown muzzle, or entirely brown, there being two color phases, 



the cinnamon bear of the northern Rockies being the brown phase; 



18 



