CHELONTA. 79 



generally, is a question which will require for its determination a more perfect 

 specimen than the fossil under description. The thickness, however, of the fractured 

 posterior part of the postfrontal indicates that the bone had been broken not very 

 close to its natural posterior border, on the supposition that this was free, as in the 

 Eraydians generally ; and the part of the suture of the postfrontal with the parietal 

 which has been pi-eserved, extends obliquely outwards and backwards, as in Po- 

 docnemys expansa, not directly backwards, as in most of the Emydes with open temporal 

 fossae. (Compare Cuvier, loc. cit., fig. 10 with fig. 14, the suture between _^ and //.) 

 With respect to the parietal bones (-), these are too much mutilated to show more than 

 the position and extent of the coronal suture. 



A few words may be perhaps expected relative to the difference which the fossil 

 in question presents to the land-tortoises. In comparison with the skull of a Testudo 

 indica of corresponding dimensions with the fossil, the larger proportional size of the 

 orbits distinguishes the skull of that terrestrial species almost as sti'ongly as the same 

 character does the skull of the marine turtles. But in addition to this, the malar bone 

 forms a larger proportion of the back part of the orbit in the Testudo, and the 

 prefronto-nasal part of the skull is more bent down ; the suture between the frontals 

 and prefrontals describes a curve convex forwards in the Testudo, whilst it deviates 

 very little from a straight line in the fossil, and that little is convex backwards. The 

 extent also of the upper surface of the postfrontals and parietals, so far as these are 

 preserved in the fossil, is greater than the whole of those bones in the land-tortoise 

 compared. 



Having been led by the foregoing comparisons to refer the fragment of the fossil 

 skull (PI. 40, figs. 1,2) to the family Paludmosa, it is reasonable to conjecture that 

 it may have appertained to some one of the large Emj'^dians, which we already know 

 to have left their carapaces in the Eocene clay of Sheppy. One commonly finds in 

 the recent skeletons of Eraydians, that any particular character of the, exterior surface 

 of the bones of the trunk is repeated on the upper surface at least of the bones of the 

 head. This comparison, in the present instance, indisposes me to regard the fossil in 

 question as having belonged to the Em//s Jevis, or to the Emys bicarinata, or to the 

 Platemi/s BuUockii with the punctate plastron. I should be rather led to select the 

 Platemys Botocrhankii from the character in question, as exhibited by the carapace and 

 plastron described at p. 66. But in provisionally registering the fossil skull in question 

 under the name of Platemys Bowerhankii, I should wish to be understood as by no 

 means vouching for the accuracy of the reference. The conjecture rests solely on the 

 character above referred to, which is far from being decisive ; and its only value is, 

 that it happens to be the only one by which Ave can be guided at present in forming 

 any opinion at all as to the specific relations of the fossil in question. 



