1908.] 



OKAPI AND GIRAFFE. 



329 



Double Zygapophysial Articular Surfaces ix Okapi. 



The posterior face of cerv. 7 and the anterior face of dors. 1 of 

 the Powell Cotton skeleton of Okapi are drawn in text-fig. 64 in 

 order to show a remarkable condition of the articular sui'faces Avhich 

 bring these two vertebrae into relation. Whilst cerv. 6 of Okapi 

 has only the usual single pair of anterior and posterior articular 

 facets, common in cervical vertebrae, and situated on the 

 zygapophyses themselves, the seventh cervical of this specimen of 

 Okapi shows on the posterior face an additional mediad pair of 



GIRAFFE, 



Text-fig. 67. 

 GIRAFFE 



Dors. 2. 



GIRAFFE 



Dors. 2. 



POSTERIOR FACE. 



ANTERSOR FACE. 



POSTERIOR FACE. 



A similar view to that given in text-fig. 66 of the corresponding vertebra; of the 

 Giraffe. The posterior face of dorsal 1 and the anterior face of dorsal 2 show 

 duplicated facets (Ls.p. and ni.s.p., l.s.a. and ni.z.a.) unlike dorsal 1 and 

 dorsal 2 of Okapi, but liJce cervical 7 and dorsal 1 (see text-fig. 64) in that 

 animal. The lateral element, however, entirely disappears from the articular 

 surfaces connecting dorsal 2 and dorsal 3, as shown by the view of the posterior 

 face of dorsal 2. 



Letters as in the preceding text-figures. 



articular facets quite distinct from the lateral pair (text-fig. 64, 

 m.s.p., cerv. 7), whilst the anterior face of dors. 1 drawn in the same 

 figure shows two articular surfaces on the anterior face (l.z.a., 

 m.z.a.). 



If we pursue the enquiry as to the articular surfaces, we find 

 on examining the posterior face of dors. 1 and both faces of dors. 2 



