48 



THE PKJEVALSKY HOESE. 



measured in the Tari^an. Their size in E. ijrjevalshii is as 

 follows : — 



Lumbar vertebrae. 



Length of centrum 



Width between the ends of the transver.se 1 

 processes ... ... ... ... | 



Length of spinous process 



Width of centrum 



Width of articular processes ... 



Fig. i8. — Sacrum (dorsal aspect). 



THE SACRUM (Fig. 18), which consists of five fused vertebrae, 

 entirely corresponds in form, in size, and in the arrangement of 

 its spinous processes with the same bone of E. cahallus. It is 

 broad, on a level with the transverse processes of the first segment, 

 and does not narrow so much towards the caudal end as it does 

 in the ass (the difference in the total width of the first vertebra 

 and that of the last segment is as 177:50 in E. jJfjevalskii, that 

 is, the bone narrows about three and a half times ; while in the 

 ass the difference is as 130 : 29, that is, the narrowing amounts to 

 more than five times). The spinous processes are all free. That 



