THE FOSSIL JAWS FROM STONESFIELD. 7 



pointed tubercles upon the inner edge. ThOse specimens of 

 this fossil which are completely disengaged from their matrix 

 probably exhibit a similar conformation of their molar teeth; 

 for M. Agassiz says in his note, that the grinders have five 

 points, disposed like those of the Insectivora. The curve of 

 the horizontal ramus of the Didelphis Bucklandii, and the 

 form and direction of the ascending one, present a perfect 

 agreement with that of the D. murina ; the differences con- 

 sist in the fossil having the condyle less elevated, the tongue- 

 shaped process of the angle more external, and the opening 

 of the dental canal more anterior. 



The Didelphis Prevostii has the ramus of the jaw straight- 

 er, but the form of its molars, and the great number of these 

 teeth, bring it nearer to the didelphs than to any other mar- 

 supial animal. 



If we compare the fossil animal with the Insectivora, we 

 perceive in the latter the coronoid process carried more for- 

 ward, and separated from the condyle by a deeper space ; 

 the angular process of the jaw is shorter, forming a less ob- 

 tuse angle with the horizontal ramus ; the commencement of 

 the horizontal ramus is more convex, the rest of the bone 

 straighter, and the number of teeth always less. 



Nevertheless, if we admit that the fossil animal is of the 

 order of Marsupialia, we must not wonder at the resemblance 

 which may exist between it and the Insectivora, for we know 

 that the pouched animals form a kind of sub-class, as Cuvier 

 says, of which the series is parallel with that of the placental 

 Mammalia ; and we can thus distinguish insectivorous mar- 

 supials, carnivorous marsupials, and rodent marsupials ; 

 &c. But the animals of this order [Marsupialia] are the only 

 the Cetacea excepted, which are furnished with so large a 

 number of teeth. 



It was also thought that this fossil animal might be refer- 

 red to the family of the seals, on account of the subdivision 

 of the teeth into lobules. I shall first observe, that in the 

 Phoca properly so called, the common seal is the only one 

 which has five tubercles upon the dental crown ; — that the 

 others have only three ; — and that in the Phoca cristata there 

 even appears to be nothing more than a simple, blunt, coni- 

 cal crown, furrowed upon its surface, and without any sup- 

 plementary tubercles. 



Thus, a lobulated form of tooth cannot be looked upon as 

 a constant characteristic of the seals, and consequently is not 

 a distinction of importance. But it must be observed that 

 among the Amphibia the angle of the jaw is not produced in- 

 to the tongue-shaped process which exists among the car- 



b 4 



