LYON] THE HARES AND THEHi ALLIES 4^3 



and narrow, as it is throug-hout the other Leporidas, but devoid of 

 any ventral keel. A slight ridge indicating a keel is seen on the 

 ventral face of the expanded portion however. The mesostcrnum in 

 general is very like the same structure in Limnolagiis. The first and 

 second segments are subequal, the third and fourth segments are 

 subequal in length, but the fourth is broader. Both of the latter 

 are relatively wider than they are in Limnolagiis and as in that genus 

 are firmly ankylosed. The xiphisternum is long and rather stout. 

 It is but a little shorter than the whole mesosternum and decidedly 

 longer than the presternum. The seventh pair of ribs does not meet 

 the sternum, but articulates only with the cartilages of the sixth pair. 



The ribs (pi. xciv, 8) of Roiiicrolagns are very similar in structure 

 to the ribs of Pronolagits; the only marked difference is that the 

 poorly developed spine-like portion of the tubercles is last found 

 on the sixth pair of ribs instead of on the seventh pair. The shafts 

 of ribs are relatively narrow, and there is no indication of the wide 

 expansion found in Lcpiis. Decidedly the widest part of the ribs is 

 behind the spine. 



Shoulder Girdle and Upper Extremity. — The ratio of the length 

 of the humerus to the length of the clavicle (pi. xcvi, i) in Romero- 

 lagus is 3.2, in Oryctolagus 3.15, in Sylvilagns 4, in Ochotona 2. In 

 the skeletons representing the other genera the clavicles have been 

 lost, due to faulty preparation. In the original account of the 

 genus Romerolagus, the description reads (Merriam '96, p. 171) : 

 " The clavicle is complete and articulates directly with the sternum 

 (fig. 33), a thing that never happens in the genus Lepus." In the 

 present condition of the skeleton of Romerolagus, the clavicle has 

 been cleaned from all its attachments. An examination of uncleaned 

 skeletons of Oryctolagus and Sylvilagus showed that the clavicle 

 did not articulate directly with the sternum. In the articulation of 

 the clavicle Romerolagus resembles Ochotona, and not the other 

 genera of the Leporidas. 



The scapula (pi. xcvii, 9) of Romerolagus differs in form from 

 the scapulae of the other Leporidae, except Pronolagus, with which it 

 has many points of similarity. It is long and narrow, its posterior 

 border is practically straight instead of being concave, as in the 

 other genera; its superior border is straight rather than convex. 

 The distance between the antero-superior angle and the postero- 

 superior angle is contained twice in the length of the scapula 

 measured along the inner surface at the attachment of the spine. In 

 the other genera with the exception of Pronolagus the distance be- 



