3^6 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vOL. 45 



That part of the transverse process of the thoracic vertebra 

 which articulates with the tubercle of the rib is the same in form in 

 the two families. Associated with this transverse process in the 

 Ochotonidae are the metapophysis and the anapophysis. Both 

 these processes are first seen on the third thoracic as mere tubercles. 

 The anapophysis grows larger on each successive vertebra, attaining 

 its greatest size on the last thoracic. From the eleventh thoracic 

 onward, the anapophysis is a well-marked process directed upward, 

 backward, and outward. The metapophysis remains little mor^ 

 than 'a tubercle until the tenth thoracic vertebra is reached, where it 

 is a well-marked process. On the eleventh it is slightly larger, and 

 on the twelfth still larger but closely associated with the prezygo- 

 pophvsis. The metapophysis scarcely increases in size through 

 the rest of the series and continues closely asociated with the pre- 

 zvgopophysis throughout. Xo ventral spines or hypophyses are 

 found on any of the vertebrae. Some of the posterior thoracic have 

 a slight ventral ridge which is also found on all the lumbar vertebrae. 



Lumbar Vertehrcc (pi. xciv, lo). — Corresponding to the greater 

 number of the thoracic vertebrae in the Ochotonidae, there is a 

 diminution in the number of the lumbar vertebrae, from 7 to 5, but 

 this is not sufficient to make the number of thoraco-lumbar ver- 

 tebrae the same in the two families. The lumbar vertebrae of Ocho- 

 tona are very different in form as w^ell as in number from those of 

 Lepiis and its allies. Each vertebra is compact, with the processes 

 broader and more closely applied to the body instead of the slenderer 

 processes extending to a distance from the centrum such as occurs 

 in the Leporidae. The neural process is low, with the free edge as 

 long as the whole length of the vertebra and parallel with the axis of 

 the vertebra. The metapophyses are well developed and more 

 closely associated with the prezygopophyses than they are in the 

 Leporidae. Anapophyses are well developed on the first and second 

 lumbar vertebrje and are a direct continuation of the thoracic series 

 of anapophyses. These processes are slightly indicated on the third 

 lumbar vertebra, after which point they disappear. The transverse 

 process is little more than a tubercle on the first and second lumbar 

 vertebrae, but on the third and fourth it is a wide quadrilateral plate 

 of bone coming from the whole side of the vertebrae, sloping down- 

 ward and outward. The transverse process of the fifth and last 

 lumbar is a trifle longer than the other transverse processes and only 

 about half as wide, the narrowing taking place chiefly at the expense 

 of the posterior half of the process. There are no hypophyses, but 

 all the lumbar vertebrae (as is the case of those lumbar vertebrae of 



