Family LEPORIDAE 191 



Skulls 



1. Supraorbital processes each with the posterior projection 



well separated from the braincase, fig. 103a, b\ base of 



skull fenestrated 2 



Supraorbital processes each with the posterior projection or 

 extension partly or completely fused to braincase, fig. 103c, 

 d ; base of skull not fenestrated 3 



2. Nasals gradually narrowed from base to near apex; pos- 



terior projection of each supraorbital process narrow, fig. 



103a domestic rabbit, Oryctolagus cunicullts 



Nasals almost parallel from base to near apex; posterior pro- 

 jection of each supraorbital process broad, fig. 103b 



white-tailed jackrabbit, Lepus toivnsendii 



3. Each supraorbital process with part of posterior projection 



fused to braincase, leaving a distinct slitlike opening, 



fig. 103c eastern cottontail, Sylvilagus floridanus 



Each supraorbital process with posterior extension almost 

 entirely fused to braincase, leaving only a small pore, fig. 

 103d swamp rabbit, Sylvilagus aquaticus 



LEPUS TOWNSENDII Bachman 

 White-Tailed Jackrabbit 



Description. — The white-tailed jackrabbit, fig. 104, is much 

 larger than either the eastern cottontail or the swamp rabbit. 

 The upper parts in summer are buffy or brownish gray, in 

 winter white; the under parts are w T hite, except for the throat, 

 which is buff. The ears are long and tipped w r ith black. The 

 tail is white. The hind legs are long, and the feet are well 

 furred. 



Length measurements: head and body 19-20 inches (475-505 

 mm.); tail A-Al 2 inches (100-115 mm.); over-all about 24 

 inches (575-620 mm.) ; hind foot 5^-6 inches (138-153 mm.) ; 

 ear from notch 4-AVz inches or about 3)4 inches dry (96-113 

 mm.). Average weight: about 7 pounds. 



The skull is about 95 mm. (3*4 inches) long; the rostrum is 

 greatly fenestrated. The bullae are comparatively large; the 

 interparietal is fused with the parietals (unfused in Sylvilagus) ; 

 and the posterior projection of each supraorbital process is free 

 (not fused to the braincase). fig. 103/;. Dental formula: I 2/1, 

 C 0, Pm 3/2, M 3/3. 



Life History. — The w T hite-tailed jackrabbit makes its home 

 in open country, where with its large ears it can hear approach- 

 ing trouble from a considerable distance and with its long legs 



