Peterson: The Osteology of Promerycochcerus. 175 



there are seven lumbar vertebrae, a difference of considerable impor- 

 tance, as we shall presently see. 



The First Lumbar. — In the type and also in No. 1079 the lumbar 

 vertebrae are all in position and all interlocked by their zygapophyses. 

 Furthermore, they are interlocked with the dorsal and the sacrum 

 (see PI. XXXIII). The transverse process of the first lumbar vertebra 

 is longer and broader than on the last dorsal. The latter feature 

 together with the absence of a facet for a rib on the centrum are the 

 only characters worthy of mention. 



Fig. 21. 



Fig. 22. 



21 22 



Lateral view of the second lumbar vertebra of Promerycochcenis carrikeri. 



No. 1081; \ nat. size. 

 Lateral view of the third lumbar vertebra of Promerycochcerus carrikeri. 



No. 1081; \ nat. size. 



The Second Lumbar (Fig. 21). — -The anterior part of the keel on 

 the ventral face of the centrum of this vertebra is particularly deep 

 and rugose. It rapidly decreases in prominence behind, thus causing 

 a sharp emargination on the under surface and terminates posteriorly 

 in a small tubercle. The transverse process is thin and is broadened 

 distally so that it projects outward, forward, and backward. The 

 posterior face of the right transverse process has formed a strong 

 sutural contact with the anterior face of the process in the succeeding 

 vertebra, which is purely a pathological character. The mammillary 

 process is directed upward, outward, and backward and the neural 

 spine is slightly inclined forward, which is true of all the lumbar 

 vertebrae. 



The Third Lumbar (Fig. 22). — The third lumbar vertebra is similar 

 to the second in nearly all particulars and needs no further description. 



The Fourth and Fifth Lumbar s (Fig. 23). — The centra of these 

 vertebrae are more compressed laterally and the ventral keels, especially 

 in the fifth, are more regular than in the two preceding vertebrae. 



