the Fossil Jaws of Stonesjield. 653 



however add, that there yet remains something to be cleared 

 up with relation to it, for it is difficult to allow that the three 

 first molars can be analogous to the anterior teeth of the Did. 

 Bucklandii, of which Mr. Broderip makes incisors and a 

 canine tooth ; and we have as yet no example of a genus of 

 mammals in which the number of the molars thus increases 

 all at once by three on each side. 



As to the question of knowing under what order, family, 

 and even genus of Mammalia the animal must be ranged, 

 which these fossil jaws of such great antiquity reveal to us, 

 we have I think placed it beyond all doubt, that it could not 

 have been an insectivorous didelph or monodelph, the den- 

 tal system being so entirely different. The form of the mo- 

 lars seems to approach much more to that of the seals, in 

 which they are as in this case, pretty nearly alike, and fre- 

 quently tricuspid ; but the anterior part of the dental system 

 of the Stonesfield fossil, differs widely from what is found in 

 the family of the Carnassiers ; so that in the hypothesis of 

 its ranking as a Mammal, we dare not pronounce upon its 

 family and order. It seems more probable that this animal 

 must form a distinct genus, to which might be given the name 

 of Heterotherium, or Amphitherium, in order to avoid the in- 

 ductions which might be drawn from the existence so far 

 back, of a Mammal of the family of opossums. 



But if, in allowing our inquiry to be conducted by analo- 

 gous reasoning, and admitting all the evidence furnished by 

 figures and descriptions as incontestable, as for example, the 

 form and proportions of the three parts of the ascending ra- 

 mus, we have been led to infer, in establishing our comparison 

 with existing animals, that this must be a mammal sui gene- 

 ris ; would it be the same were we to carry on the compa- 

 rison to certain fossil genera ? To this question we must re- 

 ply in the negative. In fact M. le D. Harlan of Philadelphia 

 described and figured many years since, some gigantic fossil 

 bones, which he referred to a new genus of the class Reptilia, 

 named by him Basilosaurus. Now a portion of the jaw of 

 this animal displays implanted teeth of two kinds, the first 

 simple, among which there are even some resembling canines 

 larger than others ; the second compressed, triangular, and 

 provided with two roots, fixed in the jaws, and projecting 

 beyond their edges ; and as at the slightest glance we cannot 

 refuse to acknowledge their great analogy to what is described 

 and drawn of the Stonesfield animal, making the further ob- 

 servation that the teeth and the jaw which holds the former 

 are like the latter so imbedded in the matrix, that they seem 

 to form a part of it; so that at their first appearance, M. Har- 

 lan considered these bones as having belonged to an aquatic 



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