104 



ON THE EXTINCT MAMMALIA OF 



The specimen nearly agrees in its size, general form and proportions with the cor- 

 responding part in the nearly entire skull of 0. major, previously described. The 

 posterior ends of the nasals are more obtuse and, apparently in consequence of their 

 less prolongation backward, the forehead is rather longer in the median line. 



The measurements of the specimen are as follows : 



Length efface from post-orbital margin to incisive alveoli, 



Length of alveolar border, .... 



Length of upper molar series, 



Length of upper true molar series, . 



Antero-posterior diameter of last molar, 



Transverse diameter of " . . 



Depth of lower jaw below first true molar, . 



Length of lower premolar series, including lower canine, 



Length of lower premolar series, excluding " 



Breadth of first premolar. 



Breadth of second "... 



Breadth of third "... 



Breadth of first molar. 



Breadth of crown of lower canine, . 



Lines. 



60 



GO 



45 



242^ 



10 



101 



19 



23 



17 



5i 



6 



6J 



6i 



On several reniarlcahle specimens of shuUs not readilij referahle to the preceding species 



of Oreodon. 



Three specimens of skulls, exhibiting remarkable deviation in character from those 

 pertaining to the preceding species of Oreodon, probably represent as many distinct 

 species. I was at first inclined to consider them as representing accidental varieties, 

 pertaining to 0. gracilis and 0. major, though they partake of the character of the 

 other species. One of the skulls approximates in size that of 0. Gulbertsoni, but pre- 

 sents more of the anatomical peculiarities of 0. gracilis. I have suspected that it 

 might belong to a hybrid of these species, but now view it as distinct, with the name 

 of Oreodon ajjinis. 



Another skull indicates an animal as large as Oreodon major, v/lih teeth as large as 

 those of 0. Gulbertsoni, but with other characters approaching it to 0. gracilis. This 

 I have also considered to be a hybrid variety, and have named it Oreodon hyhridus. 

 The third skull resembles that of 0. Gulbertsoni in every respect, except that it is 

 provided with auditory capsules proportionately as large as those of 0. major. To 

 this variety I have given the name of Oreodon bullatus. 



Dr. Hayden reports these three skulls to have been derived from the lowest bed of 



