Fes., 1912. Mammats or ILtInois anpD 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 cecum is present in all of our species 
except those belonging to the Urside, Procyonide and apparently the 
Mustelide. The uterus is bicornate; placenta deciduate and usually 
zonary; the mamme 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 FELIDZ. Cats, p. 277, 
B. Form dog-like; claws non-retractile and not strongly curved. 
Family CANIDE. Wolves, Foxes, etc., p. 296. 
GROUP 2. Plantigrade or semi-plantigrade mammals. 
Part 1. Tail annulate (marked with alternate transverse light and dark rings) 
A. Tail bushy; molars — Family PROCYONIDE. 
Raccoons, p. 391. 
Part 2. Tail never annulate. 
A. Size very large; molars = Family URSIDZ. Bears, p. 396. 
B. Size variable; molars — Family MUSTELIDA. 
Otters, Minks, Weasels, Skunks, Badgers, and Wolverine, p. 327. 
Family FELIDZA. 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. 
