the Fossil Jaws of Stonesfield. 647 



bly upon them ; and that they have below a large dental 

 canal, their summit being truncated by the dental orifice. 



As we may have occasion to compare the fossil jaws from 

 Stonesfield with those of the placental Insectivora, let us ob- 

 tain an insight into the structure of the jaw of the Tupaia, 

 which appears most closely to resemble the fossils, especially 

 the Did. Prevostii of Cuvier ; although the maxillary bone 

 and its dental system among the tenrecs comes nearer to 

 what we have just described in the opossum. The jaw of the 

 Tupaia is in fact rather short, or moderately elongated in its 

 horizontal ramus, which is attenuated in front; with both 

 its edges slightly convex. The ascending ramus, which is 

 also of moderate size, is upon the whole very wide at its pos- 

 terior edge, and dilated into a kind of fan with three branches, 

 of which the narrow and rather curved summit of the coron- 

 oid process, and the transverse condyle and the somewhat 

 hooked angular process, bear some resemblance to the han- 

 dle of a crutch. The condyle is moreover considerably high- 

 er than the dental line. 



The dental system consists of a very nearly continuous 

 series throughout, in which, however, we can easily distin- 

 guish three long incisors, directed forwards, and rather spa- 

 tulate ; a canine, which is almost straight and subcylindrical, 

 and but slightly pointed ; and finally six subcontiguous mo- 

 lars, two anterior, one principal, and three posterior ; of the 

 two front molars with the crown almost simple, the first has 

 one and the second two roots : the principal is of moderate 

 size, and has two blunt points anteriorly, and a posterior pro- 

 cess; and lastly, the three hinder molars have an almost square 

 crown, formed, as in the Insectivora generally, with an ante- 

 rior half more elevated than the posterior, trihedral, with three 

 tubercles ; the posterior half having two, except in the last, 

 which has but one, and is rather smaller than the two pre- 

 ceding it. 



Let us now proceed to establish a comparison; and we 

 will begin with the fragment which constitutes the Did. Pre- 

 vostii of M. G. Cuvier. 



I shall not occupy much time in considering the form of 

 the ascending ramus and its three processes, because it is 

 certain that the jaw is mutilated in this part ; and if we may 

 put absolute confidence in the representation of it given by 

 Dr. Buckland, there is no doubt that, except in the position 

 of the condyle which is in the plane of the dental line, the 

 same as in the Did. Bucklandii, and contrary to what takes 

 place in the opossums, as well as in the Insectivora, — this 

 branch bears scarcely any resemblance to that of Did. Buck- 



