176 



Annals of the Carnegie Museum. 



The transverse processes are branched distally, the larger portion 

 projecting outwards and forwards and the smaller portion outwards 

 and backwards. 



23 24 



Fig. 23. Lateral views of the fourth and fifth lumbar vertebrae of Promerycochoerus 



carrikeri. No. 1081; \ nat. size, i, fourth; 2, fifth lumbar. 

 Fig. 24. Lateral view of the sixth lumbar vertebra of Promerycochoenis carrikeri. 



No. 1081; -3- nat. size. 



The Sixth Lumbar (Fig. 24). — The centrum of the last lumbar 

 vertebra is, as usual, more depressed and has a greater transverse 

 diameter than those preceding it. The ventral surface of the centrum 

 is broader with the keel not so sharp as in the preceding vertebrae. 

 The transverse process is relatively much longer than in the corre- 

 sponding vertebra of Merycoidodon ciilbertso7ii; it is also much ex- 

 panded distally and there is a protuberance on the posterior extremity 

 which articulates with a corresponding surface on the anterior ex- 

 tremity of the pleurapophysis of the first sacral vertebra not unlike 

 what is seen in the hippopotamus. An entirely different arrangement is 

 observed in the transverse process of the last lumbar in Merycoidodon, 

 in which the process is much reduced when compared with those in 

 front of it. This reduction in size does not appear to be brought about 

 in order to unite with the sacrum by forming the usual articular 

 surfaces between the process and the ilium, but is simply an adjust- 

 ment to the limited space which exists between the anterior portion 

 of the ilium and the centrum of the vertebra. On the posterior ex- 

 tremity of the process is a protuberance, which abuts against the 

 pleurapophysis of the first sacral as in P. carrikeri. The neural spine 

 of the sixth lumbar vertebra of the latter species is smaller than on the 

 vertebrae immediately preceding it, but the antero-posterior diameter 

 is relatively greater than in Merycoidodon. In general the centra of 

 the lumbar vertebrae of Promerycochoerus are less depressed and the 



