Troxell — Vertebrate Fossils of Hock Creek, Texas. 617 



The limbs of the Yale specimen are heavy ; the hoofs are 

 about a sixth broader than those of the Arabian horse of to-day. 

 The skull is heavy. E. scotti was a ponderous animal, a form 

 not suited to rapid movements but one probably living in a 

 region surrounded by luxuriant vegetation with plenty of food 

 and water and close in its habits to the mammoth and ground- 

 sloth with which it may have been associated. Gidley has 

 ascribed to the type specimen certain characters which would 

 link it with Equus asinus or E. quagga, especially in the 

 longer body, much larger head, shorter back and steeply sloping 



Fig. 3. 



Fig. 3. Posterior and ventral anterior views of atlases. 1, Equus cab al- 

 ius ; 2, E. calobatus, n. sp.; 3, E. scotti. About one-sixth nat. size. 



sides. The type was a young animal and therefore may show 

 characters and proportions differing from the more mature 

 Yale specimen, thus more closely resembling the ass and 

 quagga. 



There are, however, a number of characters shown by the 

 Yale specimen which indicate a very close relation to Equus 

 caballus and a distinct separation from Equus asinus. The 

 ratios between Equus scotti and the smaller Arabian horse run 

 with unusual constancy and give the average of 88*8 per cent. 

 The characters of the sacrum, especially in the manner in 

 which the dorsal and ventral foramina enter the neural canal 

 (fig. 5), the general form of the atlas (tig. 3) and the ratios of 

 the skeletal parts, all show a great similarity of E. scotti to 

 E. caballus. The width of the muzzle measured across the 

 alveoli of incisors number three is greater than the width 

 across the premaxilla over the canines. This is a horse char- 

 acter, distinguishing it from the ass. 



Applying the principles of Craniometry, the skull is shown 

 to be exceedingly like that of the recent horse, E. caballus, 

 sometimes surpassing the average horse in the extreme of horse 

 eccentricities, and again showing a slight tendency to some of 

 the characters of the mule. 



