DAKOTA AND NEBRASKA. 



231 



occupy an inch and a half less space than the true molars ; in the B. occidentalis, 

 eleven lines less. 



The lateral incisors have a different shape from those of R. occidentalis, and are 

 proportionately better developed than in the Indian Rhinoceros. The fang a little 

 below the base of the crown is cylindrical, and about ten lines in diameter. The 

 crown is conical, and is worn off internally in a long triangular slope. In its present 

 condition it measures an inch and a half in length, by ten lines in width fore and aft 

 at the base, and eight and a half lines transversely. 



The sockets for the internal incisors indicate their occupants to have held about 

 the same relation in size to the lateral incisors as in the Indian Rhinoceros. 



The size of the jaw of the California Rhinoceros appears to be too small to belong 

 either to R. crassus or R. meridianus, and it is therefore inferred to be a distinct 

 species, for which the name of R. hesperius has been proposed. 



Measurements derived from the lower jaw, in comparison with those of Professor 

 Hall's specimen of the lower jaw of R. occidentalis, are as follow : 



R. hesperius. R. occidentalis. 



From back of last molar to incisive alveoli, 



Depth below last molar. 



Depth below second premolar, 



Depth of symphysis, . 



Breadth of chin outside of canines, 



Length of series of six large molars. 



Length of true molar series, 



Length of premolar series, exclusive of the first 



Length of hiatus in advance of molars, 



Breadth of last molar, . 



Breadth of second molar. 



Breadth of first molar. 



tooth, 



Lines. 



Lines. 



132 



108 



34 



26 



30 



22 



52 



34 



32 



20 



78 



73 



48 



42 



30 



31 



30 



22 



17 



16 



16 



15 



14 



Hi 



Quite recently (Feb., 1869) Prof. Whitney submitted to my examination a 

 number of fragments of upper molar teeth, together with the entire unworn crown of 

 one, probably belonging to R. hespei-ius. They are reported to have been discovered 

 in association with human and equine remains in Calaveras Co., California. 



The teeth evidently pertained to a species approaching nearly in size the R. occi- 

 dentalis, of Dakota. The entire unworn crown above mentioned is that of a last 

 molar from the left side of the upper jaw, and closely approaches both in size and 

 form the corresponding tooth of R. occidentalis, as represented in plate XXII. It 

 differs, however, in having the anterior lobe much more strongly constricted near its 



