442 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 53. 



obliquely directed forward and outward, as in E. lamhei, but has 

 its anterior end turned inward so strongly that the metastylid is 

 nearly cut off from the metaconid. The hinder end of the loop is 

 likewise turned more or less outward. 



The outer incisor tooth of the jaw here described appears to have 

 been quite different from that of the type of E. lamhei. Although 

 this incisor in the type is worn until the bottom of the cup has 

 passed, there are yet indications of its former presence. In this in- 

 cisor of the odd jaw the cup is replaced by a broad groove on the 

 hinder face of the crown. 



It is believed that this odd jaw belongs to a species distinct from 

 the type E. lamhei., but it is perhaps better to await further dis- 

 coveries before giving it a name. 



In any studies of the animals found in Alaska and Yukon it is 

 important that we consider ca,refully the related species which are 

 found in northeastern Asia. 



In 1893 ^ J. Tscherski described a well-preserved skull of a horse 

 which had been obtained at Liakhof Island, in the Arctic Ocean. 

 This skull he referred to Equus caballus. Many measurements taken 

 from this skull are given on pages 333 and 334 of Tscherski's paper. 

 The basilar length was 502 mm. ; the facial width, 216 mm, ; the dis- 

 tance from the rear of the orbit to the incisive border, 381.5 mm.; 

 the width of the face at the maxillo-malar suture (width of cheeks), 

 191 mm. ; the length of the upper tooth line, 175 mm. 



The cephalic index of this skull is therefore 43. The facial length 

 may be estimated from the right angled triangle formed by the half 

 of the frontal width and the distance from the incisive border to the 

 rear of the orbit. It is 365.8 mm. The f acio-cephalic index is there- 

 fore 72.6. On account of injury done to the occipital crest the vertex 

 length and the cranial length could not be obtained. Hence the 

 cranio-cephalic index can not be determined. The index of the tooth 

 line (molar-premolar length X 100 -^ basilar length) is 34.9. If 

 these fundamental measurements and the indices of this Siberian 

 skull and that from Yukon are brought together they may be easily 

 compared. 



Table of measurements and indices. 



1 Mem. Acad. Sci. St. Petersb., vol. 40, p. 335, pi. 5 ; pi. 6, flg. 5. 



