and Picas in the British Museum. 221 
strong. Skull high, more or less compressed ; the nose arched ; 
maxille netted in front of the orbits. Cutting-teeth (upper) 
with a subcentral groove ; molars 3° 2, each formed of two plates 
united by enamel, except the upper hinder one, which is small 
and formed of only one plate. The upper hinder grinder is like 
the third plate in the former family ; but it is distinct, forming 
a separate tooth. 
Section I. Skull high, rather compressed. Nose compressed ; cheeks 
nearly flat, separated from the orbits by a strong ridge, and edged 
above by the prominent upper hinder elongated process of the in- 
termazillaries. Orbits large, roundish. Cutting-teeth moderate. 
A. Hares. The hinder nasal aperture of skull broad, deep, 
rounded above, and with nearly erect sides. Young born with 
the eyes open and the body covered with hair. Living in “ forms”’ 
on the surface of the earth. 
1. Postorbital process more or less soldered with the skull. 
1. Hyproxacus. Lepus § F, Baird, N.A.M.575. Feet very 
short, weak, covered with scattered hairs, exposing the toes ; claws 
acute. Skull and incisors comparatively large and massive; muzzle 
about as wide as high. Postorbital process completely fused 
into the skull for its entire length, leaving neither foraminal 
notch nor suture. “ Water-Hare.” 
* Tail elongate, white beneath. 
1. Hydrolagus aquaticus. (Lepus aquaticus, Bachm. J. A. N.S. 
Philad. vii. 319, t. 22. f.2; Baird, N. A. M. 612, t. 59. f. 1 
(skull). LZ. Douglasii, var. 1, Gray, Mag. N. H. 1837, p. 586.) 
** Tail very short, dusky beneath. 
2. Hydrolagus palustris. (Lepus palustris, Bachm. J. e. t. 25, 
26; Baird, N. A. M. 615, t. 59. f. 2 (skull). LZ. Douglasiz, 
var. 2, Gray, Mag. N. H. 1837, p. 586.) 
2. Sytvinacus. Lepus § D, Baird, N. A. M. 575. Skull 
about twice as long as wide, very convex and much arched be- 
hind; muzzle rather wider than high. Postorbital process mo- 
derate, united behind and laterally by anchylosis with the skull, 
with a distinct suture bounding a small narrow foramen in 
front. Cutting-teeth narrow. Hind feet nearly as long as the 
head. Burrows for protection (Clark). 
* Soles very densely furred. 
1. Sylvilagus nanus. (Lepus nanus, Schreb. t. 2348; Dekay. 
L. americanus, Desm. Lepus sylvaticus, Bachm., Waterh. Gl. 
116; Aud. N. A. Q. t. 22; Baird, N. A. M. 600, t. 58. f. 1 
(skull).) Grey Rabbit. B.M. 
