440 



MEMOIRS OF THE CARNEGIE MUSEUM. 



centrum of the first lumbar is not unlike that of the posterior dorsals, while further 

 back the lumbar vertebrae are more depressed and gradually broadened. The 

 last is broader than long. The last lumbar vertebra is otherwise conspicuous on 



Fig. 25. Dicerolhcrium cooki Peterson. No. 2470a, Coll. Carnegie Museum. Posterior view of second 



lumbar. X l- 



account of its suddenly reduced neural spine. This reduction is principally in the 

 fore-and-aft direction so that there are broad vacuities between the spines in front 

 and behind. 



The more noticeable variations in the lumbar series result from the presence 

 or the absence of an articulating buttress between the fourth and fifth lumbars. 



Fig. 26. Diceratherium cooki Peterson. No. 2470«, Coll. Carnegie Museum. Lateral and posterior 



views of lumbar four. X \. 



This articulation is located on the transverse process (posterior face) of the fourth, 

 and meets a corresponding surface on the anterior face of the process on the fifth 

 lumbar. (See figs. 26 and 27.) The first lumbar is sometimes found to possess 

 an unusually long transverse process, which tapers rapidly and is rib-like. 



