SKELETON OF PERISSODACTYLA. 



447 



the vertebral artery entering the neural canal and perforating 

 the neurapophysis, lengthwise. The transverse processes of the 

 last lumbar present each a concave articular surface to corre- 

 sponding convexities of those of the sacrum.' 



In the Horse, fig. 300, the vertebral formula is — 7 cervical, 

 19 dorsal d, 5 lumbar, a, h, c, d, e, 5 sacral,/* — I, and 17 caudal, 

 p — r. Eight pairs of ribs directly join the sternum, which con- 



sists of seven bones and an ensiform cartila^'e. The neural 



Ilorsc (Equiis cahalhis). 



arches of the last five cervical vertebra? expand above into flat- 

 tened, subquadrate, horizontal plates of bone, with a rough 

 tubercle in place of a spine: the zygapophyses are unusually 

 large. The perforated transverse process sends a pleurapophysis, 

 z, downward and forward, and a diapophysis, r, backward and 

 outward, in the third to the sixth cervicals inclusive: in the 

 seventh the diapophysial part alone is developed, and is imper- 

 forate. The neural s})ines suddenly and considerably increase in 

 length in the first three dorsals, and attain their greatest length 



' xcv, pi. viii. fig. 1 , 0. 



