334 ON THE OKAPI AND GIEAFFE. [Apr. 1 , 



The Rhinoceros is the only case in which I found actually two 

 pairs of facets marked out, almost but not quite as separate 

 from one another as in Okapi. In several specimens of this 

 genus I find that the facets between cervical 7 and dorsal 1 are 

 purely lateral : between dorsal 1 and dorsal 2 the facets are very 

 lai'ge and each is incompletely separated into a lateral facet 

 and a mediad facet. Between dorsal 2 and 3 this is even more 

 marked : there are two facets on each side of each of the 

 articulating vertebrfe. On the posterior face of dorsal 3 — and 

 the anterior face of dorsal 4 — we find only the mediad pair of 

 facets. These articulations are shown in the four drawings, text- 

 figs. 68, 69, 70, & 71. In Rhinocei-os then the transition is quite 

 gradual — from the "cervical" condition of the joint to the "dorsal" 

 condition — the articulations dors. 1 : dors. 2, and dors. 2 : dors. 3 

 showing cleai'ly the lateral or cervical facet as well as the mediad 

 or dorsal facets on each side. This observation requires of course 

 further confirmation and may prove not to indicate a rule without 

 exception when a larger series of Rhinoceros is examined. 



Thus we may tabulate the conditions in regard to this matter 

 in XJngulata as follows : — 



Normal in Ruminants : — 



ci p P 



Cerv. 7< >dors. 1. dors. \< >dors. 2. dors. 2< ^dors. 3. dors. 3. 



Okapi : — ^, 



ji CJ OJ o 



cj g p g 



Ccrv. 7< — ^dors. 1. dors. 1< — >dors. 2. dors. 2< — ^dors. 3. dors. 3. 



Cerv. 7< — >dors. 1. dors. l^-^do7's. 2. do7-s. 2< — ^dors. 3. dors. 3< — >dors. 4. 

 Rhinocekos : — da . dg . ^ 



rS CS p _« g P 



Cerv. 7< — >dors. 1. dors. 1< — ^dors. 2. dors. 2< — >dors. 3. dors. 3< — >dors. 4. 



The multiplication of artictilar facets between successive 

 vertebrae is of course well-known in another region of the 

 Mammalian vertebral column. At the lumbar end of the dorsal 

 series in the Great Anteater {Myrmecojihaga jithata) we find that 

 dorsal 12 exhibits no less than three pairs of zygapophysial facets — 

 the most dorsal and median of which, though horizontal in dorsal 

 12, becomes tilted to a vertical position in dorsal 13 and the 

 following vertebrae. 



