110 



THE MERYCOIDODON'im-E 



The twelfth dorsal has the anticlinal neural spine, complete interlocking prezygapophyses and 

 postzygapophyses, and but a trace of the rib facet on the transverse process. The mammillary 

 process above the prezygapophysial process is present in the dorsals, and in this one it is entirely 

 separated from the transverse process. The complete intervertebral foramen appears for the last 

 time. The thirteenth dorsal has lost the tubercular facets and has a strongly keeled centrum, and 

 the spine is similar to those of the lumbars. The fourteenth dorsal has a longer and heavier trans- 

 verse process and a larger and more rugose keel than the preceding vertebra. The rib facet is 

 almost entirely confined to the centrum. 



The transverse process of the first lumbar is longer and broader than that of the last dorsal, 

 and there is no rib facet on the centrum. In the second lumbar the spine is somewhat forwardly 



Fig. 70. — Promerycochccrus carrikeri Peterson. Inferior view of skull. PLT. Cat. No. 109 CM. 1/3 nat. size. (After 



Peterson, 1914.) 



inclined, as in all the lumbars. The deep and rugose keel rapidly decreases aft, thus producing a 

 sharp emargination on the inferior surface and terminating posteriorly in a small tubercle. The 

 transverse process is thin and distally broadened. The third lumbar is much like the second. The 

 centra of the fourth and fifth lumbars are more laterally compressed, and the transverse processes 

 are branched distally, with the larger portion projecting outward and forward. In general the 

 lumbar vertebra; are less depressed and the neural spines are lower, but with a greater antero- 

 posterior diameter and a greater forward inclination than in Merycoidodon. 



The sacrum has seven coossified vertebra in two of the skeletons and eight in the third. Mery- 

 coidodon generally has four. The sacrum is very robust and nearly twice as long as wide. The 

 sacral foramen is large. The neural spine of the first is free, but the others are coalesced. 



The few caudals that exist with the specimens of this species indicate a moderately long tail. 



