174 Annals of the Carnegie Museum. 



only a trace of the rib-facet on the transverse process. The ascending 

 or mammillary process over the prezygapophysial articulation is 

 entirely separated from the transverse process of this vertebra. In 

 Merycoidodon culhertsoni this separation is already established in the 

 eleventh dorsal. The intervertebral foramen is present; it is of large 

 size and separated from the posterior intervertebral notch only by a 

 thin partition of bone. The neural spine is low and has a much greater 

 antero-posterior diameter than in the preceding vertebra. 



19 20 



Fig. 19. Lateral view of the thirteenth dorsal vertebra of Promerycochcerus 



carrikeri. No. 1081; \ nat. size. 



Fig. 20. Lateral view of the fourteenth dorsal vertebra of Promerycochcerus 



carrikeri. No. 1081; \ nat. size. 



The Thirteenth Dorsal (Fig. 19). — This vertebra is very similar to 

 the one preceding it, but is characterized by the absence of tubercular 

 facets for the ribs and the distinct transverse process which is located 

 well back. The posterior border of this process is continuous with the 

 anterior border of the posterior intervertebral notch. The centrum is 

 strongly keeled and presents a triangular outline, especially behind. 

 The mammillary process over the prezygapophysis has a more upward, 

 outward, and backward position than in the preceding dorsals. The 

 neural spine is similar to those of the lumbar series. The inter- 

 vertebral notch is not developed into a foramen in this vertebra. 



The Fourteenth Dorsal (Fig. 20). — This vertebra differs from the one 

 preceding it in having a longer and heavier transverse process, a 

 greater and more rugose keel, and the ventral face of the centrum 

 convex. The facet for the last rib is almost entirely confined to the 

 side of the centrum of this vertebra. Except in the matter of the 

 latter facet it agrees quite well with the first lumbar in Merycoidodon. 



The dorso-lumbar series in Merycoidodon and Promerycochcerus are 

 equal in number, but the older genus has only thirteen dorsals while 



