DAKOTA AND NEBRASKA. 



97 



Skull of Oreodox gracilis. 



Length skull fr. summit of inion to end of nose, 



Length lower jaw fr. hack border to inc. alv., 



Length cranium from summit of inion to post- 

 orbital margin, . . . . 



Breadth of cranium where narrowest, 



Length face fr. post. -orb. margin to end of nose, 



Breadth cranium where most convex on the 

 parietals, .... 



Height of occiput or inion, 



Brea'dth of occiput at base, 



Breadth of skull at z_ygoniatic arches, 



Breadth at the post-orbital arches, 



Breadth of face at anterior orbital margins, 



Breadth of face at upper first ])remolars. 



Breadth of face above last molars. 



Length of parietal crest. 



Length of frontals in median line. 



Length of nasals, 



Breadth of snout between ends of frontal a 

 gular processes, . 



Vertical diameter of orbits, . 



Transverse " " . 



Height of lower jaw at coronoid process, 

 " " " condyle, 



" back"of last molar, 

 " " " second premolar, 



Breadth of do. obliquely back of last molar, 



Length of symphysis of lower jaw. 



Distance between the supra-orbital foramina. 



Distance between the infra-orbital " 



Length of hard palate, 



Width of hard palate between first molars, 



Length of the alveolar borders. 



Length of the upper molar series, 

 " lower " ■ " 

 " " upper true molar series, 



" lower 



The teeth of Oreodon gracilis are identical in form with those of 0. C'ulbertsoni, 

 and are ordinarily distinguishable only by the size. In those specimens, however, in 

 which the teeth of the former are fully equal in size to those of smaller teeth of the 

 latter species, independently they would be undistinguishable. 



The following table presents measurements of the upper teeth of Oreodon gracilis. 

 Those of the first and second series are taken from the same specimens as Nos. 2 and 

 3 of the preceding table, and exhibit the usual sizes. Those of the third and fourth 

 series correspond with Nos. fi and 10 of the preceding table, and present sizes greatly 

 in excess of the usual ones. Other specimens are at hand, exhibiting all gradations 

 of intermediate sizes, but none in a condition to give complete series of measurements. 

 The fifth series of the table gives measurements from a specimen of Oreodon Culbert- 

 soni with small teeth, previously indicated as No. 16 : 



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