FEB., 1912. MAMMALS OF ILLINOIS AND WISCONSIN CORY. 277 



this order; some, like the Bears, are plantigrade, walking on practically 

 the entire sole of the foot; others, like the Wolves and Cats, are dig- 

 itigrade and walk on the toes; while still others are strictly neither one 

 nor the other and are often considered as semi-digitigrade. The various 

 differences, however, will be treated under the different families and 

 genera and need not be further discussed here. 



The stomach is simple and a caecum is present in all of our species 

 except those belonging to the Ursida, Procyonida and apparently the 

 Mustelida. The uterus is bicornate; placenta deciduate and usually 

 zonary; the mammas vary in number but are always abdominal. 



KEY TO OUR FAMILIES. 



GROUP 1. Digitigrade mammals. 



A. Form cat-like; claws sharp, strongly curved and retractile 



Family FELID^. Cats, p. 277. 



B. Form dog-like; claws non-retractile and not strongly curved. 



Family CANID^). Wolves, Foxes, etc., p. 296. 



GROUP 2. Plantigrade or semi-plantigrade mammals. 



PART i. Tail annulate (marked with alternate transverse light and dark rings). 

 A. Tail bushy; molars ^3 Family PROCYONID^. 



Raccoons, p. 391. 

 PART 2. Tail never annulate. 



2-2 



A. Size very large; molars ^^ Family URSID./E. Bears, p. 396. 



o o 



B. Size variable; molars ^- Family MUSTELID^. 



2-2 



Otters, Minks, Weasels, Skunks, Badgers, and Wolverine, p. 327. 



Family FELID^. The Cats. 



This family, which is probably the most highly specialized of the 

 order, contains the Cats, both great and small, such as Lions, Tigers, 

 Panthers, Wild Cats or Lynxes, etc. 



In all the species the canine teeth are highly developed and most of 

 the cheek teeth are sharp edged, being especially adapted for cutting. 

 The claws are curved, sharp and retractile, and capable of being drawn 

 back or extended at the will of the animal. Ordinarily the claws are 

 tipped backward and are protected by a sheath, being nearly or quite 

 concealed, so that no claw marks are shown in the tracks made by the 

 animal when walking. When needed for use, they are tipped forward 

 and downward by contraction of the powerful flexor muscles. 



