lvon] the hares and their allies 3 57 



and seventh still less so, forming only a narrow arch over the 

 vertebral canal. 



Not many variations are found in the cervical vertebrae in the 

 different genera of the Leporidse, but in general two forms occur : 



First, large rabbits, in which the individual vertebrae are vmiformly 

 lengthened, and in which the costal process does not project laterally 

 from the centrum to a marked extent, and the anterior and posterior 

 spines of the costo-transverse process are more elongated. Cervical 

 vertebrae of this type are found in all the skeletons belonging to the 

 genus Lcpiis. 



Second, rabbits averaging smaller in size in which the individual 

 cervical vertebrae are uniformly shortened and in which the costal 

 process projects further laterally from the centrum than it does in 

 the first group, the anterior and posterior spines of which are less 

 pronounced. The true transverse process is slightly more con- 

 spicuous here, and often begins to project laterally from the vertebra, 

 beginning with the fifth cervical instead of with the sixth as in 

 the case of the more elongated type of cervical vertebrae. All the 

 genera of the family Leporidae, with the exception of the genus 

 Lepus, belong to this section. 



The most extreme development of the shortened type of cervical 

 vertebrai is seen in Pronolagiis, in which the costal process stands 

 out still farther from the body of the vertebra. The process is 

 narrower, that is, its antero-posterior dimensions are relatively much 

 less than they are in the other genera. The cephalad and caudad 

 projecting spines of the costal processes are apparently not well 

 developed, but they have a somewhat worn or damaged look in the 

 only specimen examined. The general appearance of the cervical 

 vertebrae in Pronolagiis, when viewed from below, is much as it is 

 in Ochotona. 



Thoracic Vertcbrcc. — There are twelve thoracic vertebra, of which 

 the more anterior are wider from side to side than they are long, 

 while the reverse is true of the posterior vertebrae. The general 

 size of each individual vertebra increases as one passes from before 

 backward. 



The centra, often at the beginning of the thoracic series and nearly 

 always toward the end of it, have a low ventral median ridge, which 

 on some of the anterior lumbar vertebras is produced into a spine, 

 the hypophysis. 



In the first eight vertebras of the thoracic series, the transverse 

 processes are well developed and each is furnished with a large 

 facet for articulating with the tubercle of the rib. In the ninth, 



