RODENTIA LEPORIDAE LEPUS. 



575 



C. Skull more than twice as long as wide ; muzzle and nasal bones very long ; the former wider than 



high, anterior to the molars; post-orbital processes divergent; not in contact behind with the 



skull L. cuniculus. 



D. Skull about twice as long as wide; very convex and much arched behind. Muzzle rather wider than 



high, post-orbital processes moderate ; united behind by anchylosis with the skull, (suture 



distinct,) and bounding a small narrow foramen anteriorly L. sylvaticus. 



bachmani. 



artemesia. 



E. Similar to preceding ; the post-orbital process not in contact with the cranium L. trowbridgii. 



auduboni. 

 . Skull and incisors very large and massive ; muzzle about as wide as high. Post-orbital process completely 



fused with the skull for its entire length, leaving neither foramen, notch, nor suture L. aquaticus. 



palustris. 



Comparative measurements of skulls. 1 



1 The measurement of length is taken with dividers, from the transverse occipital crest to the anterior face of upper incisors in most cases; to the 

 end of the nasals, the distance is somewhat less in some, though not in all. 



1 This skull belonged to a hybrid of the second generation, between L. cuniculus and sylvaticus, and exhibits in a marked degree the cranial pecu 

 liarities of both species. Thus, we have the rather short muzzle and nasal bones, with the rounded and arched cranium proper of the latter, and the 

 divergent and free post-orbital processes of the former. 



