NATURAL SCIENCES OF PHILADELPHIA. 115 



condition appears to have had neavl}^ the same construction as in 

 the genera just named. It was indeed suspected from the form of 

 this tooth that the jaw belonged to Palasosi/ops, but to a smaller- 

 species than P. 2MludoHiis, the forepart of the jaws of which have 

 not been discovered. The bottom of the S3anphjsis of the jaw 

 under examination reaches as far back as the position of the first 

 true molar, but in a fragment of PalseoHijoj-jspaludoms is seen not 

 to extend as far as the last premolar. Other differences in the 

 corresponding portions of the jaw indicate the animals to belong 

 to different genera. 



For the curious pachj^derm, first brought to our notice by Dr. 

 Carter, the name of Trogosus castoridens, or the Beaver-toothed 

 Gnawing-hog, was proposed. 



The fossil brings to our view an animal which would appear to 

 have pertained to the stock from which diverged the Rhinoceros 

 and Mastodon, the Peccar}^, and perhaps the Beaver. 



Measurements of the fossil are as follows: Length of jaw from 

 back of last molar to fore edge of symphysis, 4 inches 10 lines ; 

 depth of jaw below true molars, 1 inch 8 lines ; depth of sym- 

 physis, 2 inches 8 lines ; thickness of jaw above base, 10 lines; 

 length of molar series from position of large incisors, 4 inches ; 

 length of true molar series, 2 inches 7 lines; space between large 

 lateral incisors, 4 lines ; fore and aft diameter of large incisors, 

 9^ lines ; transverse diameter of the same, 6 lines. 



Another interesting fossil, discovered by Dr. J. Van A. Carter 

 in the same locality as the former, is the portion of the ramus of 

 a jaw of a carnivorous animal about the size of the Gray Fox. The 

 specimen contains two teeth, apparently the last premolar and 

 the sectorial molar, behind which are portions of two other teeth. 



The last premolar is larger than in the Gray Fox, and is larger 

 than the succeeding tooth, being both wider and higher. The 

 principal cusp exhiliits a feeble deuticle in comparison with that 

 on the back border in the Graj^ Fox. The heel of the crown is 

 proportionately better developed than in the latter, and presents a 

 fore and aft acute edge, from which the sides slope to the basal 

 ridge. 



The carnassial tooth is less in size than the tooth in advance. 

 The crown has the same general form as in the corresponding 

 tooth of the Foxes and Weasels. The forepart or sectorial por- 

 tion of the crown is less well developed than in the Fox, and the 

 inner cusp is half as large as the principal one. The notch of the 

 sectorial border does not end in a cleft, as in the Fox. The heel 

 or back portion of the crown is nearly half the breadth of the 

 latter, and it includes a concavity bordered by a horseshoe-like 

 ridge, as in the Weasels. 



The next tooth is rather larger than the one described, and is 

 inserted by two fangs. The forej^art of the crown is broken away ; 

 the back part has the same form as in the tooth in advance. This 

 may also have been a carnassial tooth. 

 1871.] 



