530 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.48. 



Attention may be called to the straightness of the outline of the 

 skull, from the vertex to the front of the nasals (pi. 32) . This profile 

 is quite different from that of E. niobrarensis, and its form does not 

 appear to be due to any distortion produced in restoring the skull. 



The position of the hinder border of the vomer on the midline 

 with reference to the lower lip of the foramen magnum and to the 

 hinder border of the hard palate furnishes a character by means of 

 which certain equids may be distinguished from others. On this 

 matter the readers may consult tables given on succeeding pages. On 

 account of injuries done in this region in the types of both E. 

 hatcheri and E. niobrarensis the position of the vomerine notch can 

 not be directly determined. Tests made on several skulls show that 

 the distances of this notch from the two points mentioned are 

 roughly proportioned to the distances from these two points to a 

 small foramen situated just a little above and a little in front of the 

 optic foramen. Estimates based on this assumption leave no doubt 

 that the vomerine notch of E. hatcheri was somewhat nearer the palate 

 than to the foramen magnum, and that it was considerably nearer 

 the palate in E. niobrarensis , perhaps 25 mm. nearer. In a skull 

 from Alaska described by the writer 1 and called Equus niobrarensis 

 alashae the distance from the vomerine notch to the foramen mag- 

 num is 121 mm. ; that from the notch to the hard palate is 114 mm. 

 This character may enable us to distinguish the Californian E. Occi- 

 dent alls from both E. niobrarensis and E. hatcheri. A skull of the 

 western species described by Merriam 2 was sent to the American 

 Museum of Natural History, where it has been examined by the 

 writer. The distance from the foramen magnum to the vomerine 

 notch is 122 mm. ; from the notch to the hard palate, 141 mm. Mer- 

 riam's figure of this skull 3 shows the position of the notch. How- 

 ever, from information furnished by Merriam it appears that the 

 vomerine notch is sometimes nearer the hard palate than the foramen 

 magnum. 



Measurements are here presented of the teeth, both upper and 

 lower. For comparison corresponding measurements are furnished 

 of the teeth of the type of Equus niobrarensis and those of the domes- 

 tic horse. The upper teeth of the latter species are those of No. 843 

 of the National Museum, while the lower ones are those of No. 

 174960 of the National Museum, a very large horse with basilar length 

 of 610 mm., whose upper tooth line is, however, only 1 or 2 milli- 

 meters longer than that of No. 843. 



1 Smiths. Misc. Coll., vol. 61, No. 2. 



2 Univ. Calif. Pubs., Geol., vol. 7, No. 21. 



3 Idem, p. 399, fig. 3. 



