48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 149 



anterodorsally and laterally directed metapophysis is much larger 

 than the feeble posteroventrally and outwardly directed transverse 

 process. In the succeeding dorsals the rib has but a single articula- 

 tion, with the margin of the centrum, and the higher metapophysis 

 has moved up closer to the anterior zygapophysis and is completely 

 separate from the still shorter transverse process. In the last couple 

 of dorsals, in addition to the increasing size and relatively greater 

 depth of the centrum for this portion of the series, the metapophyses 

 are broadly expanded and the transverse processes are much reduced. 

 There are no anapophyses in the sequence, and in no instance was 

 the intervertebral foramen found to be completely closed by the 

 pedicle of the arch. 



Lumbar vertebrae. — A lumbar series for both M. chamcnse and 

 M. robustum is included in the collections (see figs. 7 and 8). The 

 number is nine in the M. chamense skeleton, and the nine articulated 

 presacrals preserved in the M. robustum skeleton all seem to be 



Fig. 7. — Mcmscotherunn chamense Cope. Lumbar and four posterior dorsal 

 vertebrae (U.S.N.M. 22918), lateral view of left side. J4X natural size. 

 New Fork member, Wasatch formation, Green River Basin, Wyo. 



lumbars. Cope considered that Phenacodus had six or seven lumbars, 

 but there seem to be only four or five in the Phenacodus primaevus 

 skeleton that I examined. These vertebrae in Meniscotherium are 

 seen to be extraordinarily large in comparison with the greater part 

 of the dorsal series. The forward sloping spines and transverse proc- 

 esses increase in length posteriorly, at least as far as the sixth, and 

 these appear relatively broader anteroposteriorly in the larger of the 

 two species. The processes of the more posterior lumbars are poorly 

 preserved in both specimens. The metapophyses, beginning with 

 their separation from the transverse processes near the end of the 

 dorsal series, increase in height and strength to about the fifth or 

 sixth lumbar, and posteriorly become subdued with little or no pro- 

 jection beyond the margin of the anterior zygapophyses. Laterally 

 the zygapophyses in the lumbar series turn decidedly upward, beyond 

 which the metapophyses continue upward as well as outward and 



