VERTEBRAE OF RABBIT. 13 



rectus just above the acetabulum along a faintly-marked and rounded ridge 

 represents the acetabular border of other Rodents, such as the Beaver, and 

 shows the limit of the respective surfaces. The incisura acetabuli through 

 which the blood-vessels and nerves enter for the supply of the hip-joint is 

 reduced in size, and the rim of the acetabulum is interrupted only by a 

 linear fissure. The symphysis of the pubis is deep. 



The skull of the tame Rabbit differs from that of the wild in having 

 the roof of its brain-containing portion much flatter as measured either 

 from before backwards or from side to side than is the case in the very 

 distinctly arched calvaria of the wild variety. The lateral boundaries of 

 the same cavity as constituted by the squamous are much more wall-sided 

 than in the wild race, and instead of curving gradually into a vaulted vertex 

 they are defined or delimited off from it by largely-developed anteroposte- 

 riorly running ridges. The height of the occipital foramen is less relatively 

 to its breadth, its upper and lower borders not being emarginated into 

 secondary curves as in the wild variety. The length of the entire skull is 

 considerably greater relatively to its breadth, though not relatively to the 

 size of the entire body. This may be double that of a wild specimen, 

 whilst the absolute breadth of the skull may be identical in the two subjects 

 of comparison, and the absolute length may be less than 30 per cent, greater 

 in the tame than in the wild variety. 



The lines and processes of the cranium and lower jaw are less sharply 

 defined and sculptured than in the wild variety, and the surface of the 

 cranial bones generally is inferior in gloss and polish. The same applies to 

 the bones of the trunk and limbs in many domestic animals as compared 

 with animals of the same species in a wild state, and indeed is usually more 

 clearly appreciable than in the case of the two varieties here compared with 

 each other. 



For the possession of rootless molars by other Rodents (Octodon, Capromys, 

 most Arvicolae) ; for that of molars with short roots or with roots incomplete or late 

 to be developed, by the Agouti, by the Paca s. Spotted Cavy, by the Beaver and 

 the Porcupine ; for that of rooted molars by the true Mice and the Squirrels, see 

 Owen, Odontography, p. 401 ; and by Leporidae in their milk dentition, see 

 Hilgendorf, Monatsber. Ak. Wiss., Berlin, 1876, p. 673. 



For the presence in Leporidae of a perfect investment instead of, as in all other 

 living Rodents, merely an anteriorly placed plate of enamel on the incisors, see 

 Hilgendorf, /. c. But preparations made by Mr. C. S. Tomes suggest that this 

 perfect investment exists only in the enamel membrane of the developing tooth. 



For numerous other points of similarity between the Hares and the Cavies, see 

 Waterhouse, History of the Mammalia, ii. p. 156, 208 ; Buffon, cit. Pallas, /. c. 

 p. 29. 



For the Shoulder-Girdle of the Rodents, see Parker, Shoulder-Girdle, 1868, 

 pp. 207-210; and for the mesial prolongation of the praesternum in Lepus and 



