314 MEMOIRS OF THE CARNEGIE MUSEUM. 
of the transverse processes and metapophyses and some of the upper portions of 
the spine. Specimen No. 1708C is practically perfect except for the loss of the 
extremity of the right postzygapophysis and a fragment at the end of the spine 
(see Fig. 72). Specimen No. 1713 is a practically perfect specimen except for the 
AKG A 
EQ WF 
MZ 
— 
Fic. 72. Lateral and posterior views of the sixth lumbar of M. petersoni (No. 1703C). 2. 
loss of the anterior and posterior epiphyses of the centrum. Specimen No. 1731 
is a centrum which preserves the bases of the transverse processes and the outline 
of the pedicels. 
The sixth lumbar vertebra is characterized by the vertical compression of 
the centrum, both the anterior and posterior articulating faces of which are trans- 
versely elongated ovals in outline, the posterior face more elongated than the 
anterior face. The transverse processes are greatly produced, relatively narrower 
than in the preceding vertebree, and project slightly forward. At their outward 
extremities they are obliquely truncated behind, so as to adapt them to the anterior 
margins of the ilia, with which there is evidence that they had ligamentary attach- 
ments. The spine is relatively shorter than in the preceding vertebre and slopes 
backward to conform with the slope of the succeeding sacral vertebre. This slope 
is more marked in specimen No. 1703C, referred to M. petersoni, than in the other 
specimens, which are referred to M. elatus. 
MEASUREMENTS OF SrxtH LUMBAR VERTEBRA. 
1708, 1708C, 1713, Sit, 
: mm. mm. mm. mm. 
Greatest height from base of centrum to top of spine....................------ 245 242 242 
Greatest transverse diameter measured across transverse processes.............- 242 240 240 
Greatest antero-posterior diameter measured from front of prezygapophyses to 
backoff postzyeapophysesn seer eer Ee oA ae Oe on aE: HAG | Wit Oe 
46 Numbers in italics denote approximate measurements, the specimens being restored or broken. 
