50 OREODON. 



internal, and least so upon that postero-internal. Of the first true molar the inner 

 half alone is preserved, and presents the corresponding lobes with broad crescentic 

 surfaces of dentine. 



The socket of the fourth premolar had lost its tooth, and is now filled with 

 matrix. 



Portions of the crowns of the third and second premolars, yet remaining, indicate 

 that these teeth had not been protruded from the gums. 



From this account, it appeal's that all the permanent true molars are fully pro- 

 truded before the temporary molars are shed. 



The two entire teeth above indicated, are in this specimen a trifling degree 

 smaller than in specimens 1 and 10, and yet the fragment of skull, though not of a 

 fully adult animal, is larger than the corresponding portion of any of the preceding 

 siDecimens described. In the upper view, it appears as if it had belonged to a 

 distinct sjjecies from Oveod(y)i Culhertsonii, and had it been the only specimen in 

 the collection besides the first indicated in the list, I would have so considered it 

 without hesitation, but, from the many variations presented in numerous individual 

 cases, I am inclined to think it is only a variety. 



The forehead is unusually long and broad ; being about three-fourths of an inch 

 greater in the former direction than in the largest specimen previously indicated. 

 The supra-orbitar foramina are removed to double their usual distance from the 

 fronto-nasal suture, or rather they appear to occupy the ordinary position, while 

 the portion of the os frontis in advance of them is unusually prolonged. The 

 lachrymal depression, also, is more shallow than usual, apparently by the spread- 

 ing or expansion of the lachrymal bone ; for the outer face of this is several lines 

 higher and broader than in the preceding specimens. 



From the collection of Dr. Owen. 



MEASUEEMENTS. 



Inches. Lines. 

 Distance of infra-orbitar foramina from frontal angular processes ... 1 6 



Distance of supra-orbitar foramina from fronto-nasal suture .... 1 2 



Length of series of upper true molars ....... 1 9 



Antero-posterior diameter of last molar ....... 8 



14. A fragment of a face of a young animal, containing on both sides portions 

 of the temporary molars ; the succeeding two permanent true molars ; and, con- 

 cealed within the jaw, the last molar. 



From the collection of Dr. Owen. 



15. The greater portion of a face and lower jaw, containing all the molars 

 except one of both sides. It presents nothing peculiar, except a slight variation 

 in details of size. 



From the collection of Dr. Owen. 



