Feb., 1912. Mammals of Illinois and Wisconsin — Cory. 261 

 KEY TO THE GENERA. 



A. Interparietal not distinct in adult; postorbital process usually nearly or quite 



divergent from skull; hind foot, 5 or more inches long; our species turn 

 white in winter. Genus LEPUS, p. 261. 



B. Interparietal distinct in adult; postorbital process more or less attached to the 



skull; hind foot, about 4 inches long in our species; do not turn white in 

 winter. Genus SYLVILAGUS, p. 266. 



(For other characters see descriptions of Genera.) 



KEY TO THE SPECIES 

 WHICH MAY OCCUR WITHIN OUR LIMITS. 



GROUP I. Length of ear from skull to tip less than 4 inches. 



Color changes from brownish in summer to white in winter; tips of ears usually 

 edged with black; nape not rufous or decidedly different in color from the 

 back; total length, about 17.50 to 18.50 inches; hind foot, 5 in. (or more); 

 tail vertebrae, about 1.50 to 1.75 inches. Occurs in northern Wisconsin but 

 not in southern Wisconsin or Illinois. 



Varying Hare or Snow-shoe Rabbit. 



Lepus americanus phceonotus, p. 262. 



Rump distinctly gray or grayish, noticeably paler than back; nape usually rufous 



brown, quite different from color of back; tail vertebrae, about 2.25 to 2.75 



inches ; hind foot, about 4 inches; does not turn white in winter. 



Mearns's Cotton-tail Rabbit. 



Sylvilagus floridanus mearnsii, p. 266. 



General color brown mixed with more or less blackish; rump not distinctly gray 



or grayish; nape often tinged with rufous brown but not pronounced as in 



mearnsi; hind foot, about 4 inches; tail, about 2.75 inches; does not turn 



white in winter. Occurs in southern Illinois but not in northern Illinois or 



Wisconsin. Swamp Rabbit. Sylvilagus aquaticus, p. 271. 



GROUP 2. Length of ear from skull to tip more than 4 inches. 



Ears with black tips; tail entirely white above and below; entire length, in- 

 cluding tail, usually more than 21 inches; tail, more than 3.25 inches long. 

 Not as yet recorded from Illinois or Wisconsin, but stragglers may occur in 

 the extreme western portion of either state. 



Jack Rabbit. Lepus campestris, p. 265. 



Genus LEPUS Linn. 



Lepus Linnaeus, Syst. Nat., X ed., 1758, p. 57. Type Lepus timidus 



Linnaeus. 



Hind legs very long; ears long; tail well developed; fore feet with 

 five toes ; hind feet with four toes ; soles of feet covered with hair; clavicle 

 imperfect; interparietal not distinct in adult; supraorbitals prom- 

 inent and wing-like*; the posterior process (postorbital process) usually 



* See Fig. 2, p. 96. 



