544 



PROCEEDIXGS OF THE XATIONAL MUSEUM. 



vol. 48. 



verse processes are broken off. The following measurements are 

 secured : 



Measurements of the supposed sixth lumbar vertebra in millimeters. 



Arabian. 



Length of centrum 



Distance between extremities of lateral processes 

 Height of anterior articular surface of centrum . . . 

 "Width of anterior articular surface of centrum . . . 



Height of spinal canal, in front 



Width of spinal canal, in front 



E. 



E. 



francisci. 



hemionus. 



± 37 



37 



±185 



160 



20 



20 



37 



47 



19 



16 



24 



24 



±40 

 212 

 23 

 53 

 30 

 32 



The sacrum consists, as usual, of 5 vertebrae, and these are consoli- 

 dated. The spines are all broken away, except the first one. The 

 following measurements are secured : 



Measurements of the sacrum in millimeters. 



Arabian. 



Total length of the sacrum along midline 



Distance in front between tips of lateral processes 



Distance from outer end of one lateral articular surface for last 



lumbar to corresponding point on other side 



Width at level of front pair of foramina 



Width at level of third pair of foramina 



Width of hinder end of fifth centrum 



E. 



E. 



francisci. 



hemionus. 



173 



175 



±166 



157 



118 



122 



75 



71 



48 



45 



27 



22.5 



180 

 211 



165 

 95 

 66 

 28 



As will be observed, the sacrum of E. francisci lacks but little of 

 being as long as that of the Arabian horse. On the other hand, it 

 is much narrower. Other differences are noted. The free borders 

 of the vertebrae behind the first are in the fossil quite acute, while 

 those of the Arabian horse are thick and rounded. In the latter 

 animal the underside of the sacrum is nearly flat from side to side, 

 the free border just described rising but little above the floor of the 

 spinal canal. In E. francisci the sharp border rises at the middle 

 of the third sacral nearly to a level above the middle of the height 

 of the canal. The first vertebra of the tail is preserved. The length 

 of the centrum is 32 mm. The width across the lateral processes at 

 their hinder end is 45 mm. 



A fragment of each scapula is preserved. In each there is a trian- 

 gular piece which presents the coracoid process and the anterior half 

 of the glenoid cavity. The latter has a side to side diameter of 

 38 mm. In Equus hemionus the corresponding diameter is 42 mm. 

 The anterior border rises to a distance of 80 mm. above the lower end 

 of the coracoid. 



The humerus is represented by the proximal end of the bone of the 

 right side and the distal end of that of the left. It is impossible to 



