434 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vOL. 45 



physis grows larger on each succeeding 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 more 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, closely associated with the prezygopophysis. The metapo- 

 physis scarcely increases in size through the rest of the series and 

 continues closely associated with the prezygopophysis throughout. 



No 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. 



There are five lumbar vertebrae (pi. xciv, lo) in Ochotona, each 

 of which is compact, with the processes broad and closely applied 

 to body. The neural process is low, with the free edge as long 

 as the whole length of the vertebra and parallel with its axis. The 

 metapophysis is well developed and is more closely associated with 

 the prezygopophysis than it is in the Leporidae. Anapophyses are 

 well developed on the first and second lumbar vertebrae 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 downward 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 nar- 

 rowing 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 the Leporidae which do not 

 bear ventral spines, possess a median ventral ridge. 



The sacrum in the pikas is long and narrow, its greatest breadth 

 being contained in its length about twice. The lateral masses that 

 are attached to the ilia have sides that are nearly parallel. The 

 neural spines, so distinct and conspicuous on the sacra of the 

 Leporidae, are reduced in the Ochotonidae to form a low dorsal ridge, 

 the spines having fused with one another. The number of vertebrae 

 entering into the formation of the sacrum of the Ochotonidae is four, 

 the same as in the Leporidte. 



The caudal vertebrae in Ocliotona are eight in number in all the 

 skeletons at hand except one, which has nine. In the three American 

 specimens, the first caudal is somewhat narrowed ; the next two are 



