FAUNA AMERICANA. 129 



which encircles them ; in others they consist of 

 re-entering folds, as in the teeth of the beaver ; 

 thus displaying, in a remarkable manner, the ex- 

 tent to which this portion of the structure of the 

 teeth may differ in the same individual: in those 

 instances where the transverse plates of enamel 

 are distinct from the encircling enamel, there are 

 no grooves on the side of the tooth ; in other in- 

 stances, the sides are grooved, as in the teeth of 

 the beaver, except that portion buried in the 

 socket, which is smooth in most instances. In all 

 other details, this skull bears the closest analogy 

 to that of the beaver. The animal was full grown, 

 as is evinced bj^ the teeth and other particulars. 



Habit and Locality. Nothing further is known 

 concerning the histor}'^ of this animal, than that 

 its skull was found more than thirty years ago on 

 the shore of the river Delaware, and presented to 

 the Philadelphia Museum ; when first discovered 

 it was nearly perfect ; by rough usage it has since 

 lost the upper incisors, and part of their alveoles. 

 This cranium has been frequently examined by 

 the curious, and by them regarded as a lusus na- 

 turcB ; the characters which it presents are cer- 

 tainly unique of their kind; the bony cavities 

 communicating with the mouth, which must have 

 served as receptacles for provision, &c. distinguish 

 this skull from that of all other animals, and par- 

 ticularly the beavers, to which, in other respects, 

 it bears so near a resemblance. That it is not a 



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