102 



ON THE EXTINCT MAMMALIA OF 



Antero-posterior diameter of second molar, . 

 Transverse " " " 



Antero-posterior diameter of first molar, 

 Transverse " " " 



Antero-posterior diameter of last premolar, 

 Transverse " 



Antero-posterior diameter of third premolar. 

 Transverse " " " 



Antero-posterior diameter of second premolar, 

 Transverse " " 



Antero-posterior diameter of canine (fang), . 

 Transverse " " '•' 



Lines. 



10 



lOJ 

 8 

 9 



Gh 

 8i 

 6 



6i 

 6 

 5 

 5 

 5 



Another specimen pertaining to Oreodon major consists of the greater part of a 

 skull, without the lower jaw, of a young animal. All the temporary teeth are yet 

 retained in the specimen, but the first and second permanent true molars had pro- 

 truded, or hold their functional position. The permanent canines and last molars 

 had commenced protrusion. 



The corresponding teeth are as large as in the specimen of 0, major first described, 

 and the skull at maturity would perhaps have had nearly the same size and propor- 

 tions as in that specimen. 



An auditory bulla, preserved in the skull, has nearly the form and proportionate 

 size as in the preceding specimen. It is, however, of less uniform depth, gradually 

 decreasing in this respect forward, so as to be rather ovoid than oval. It measures 

 eleven lines antero-posteriorly, nine lines transversely, and eight lines in depth. 



The nasal bones are broad, and their posterior extremities together form a hemi- 

 elliptical outline as in 0. gracilis. The frontal angular processes are acute. 



About a dozen small fragments of jaws, with from one to three teeth, have come 

 under inspection, which appear to belong to Oreodon major. One of these, containing 

 the three upper true molars, is represented in figure 6, plate iv, of the Ancient Fauna 

 of Nebraska. The teeth are, however, smaller than in the nearly entire skull above 

 described, which also is the case in most of the fragments just mentioned, and it is by 

 no means certain that some of them, at least, do not belong to larger individuals of 

 Oreodon Culbertsoni. 



A specimen, consisting of a fragment of the upper jaw. containing the three true 

 molars, belonging to 0. major, or a large variety of 0. Gidhertsoni, in the case of the 

 last tooth exhibits the anomaly of a third lobe, crowded in the interval between the 

 two internal normal lobes. 



An upper jaw much mutilated, and containing all the molar teeth except the first 



