CHELONIA. 3 



Emydians {Emys europcea, e. g.) than it does the Podocnemys expansa. The border of the 

 prefronto-nasal bone forming the upper part of the nostril is thick and rounded ; as is 

 also the lateral border of the same cavity formed' by the maxillary. The lower part 

 of this border of the maxillary shows the suture for the premaxillary, which must 

 have presented similar proportions to the premaxillary of the Podocnemys expansa and 

 other Emydians. The shape of the frontal (n), the proportion of the upper border of 

 the orbit which it forms, and the course of its sutures with the contiguous bones, are 

 clearly indicated in fig. 2, T. XXIX. The straight line formed by the suture between 

 the frontal (n) and postfrontal (12) resembles that in the Podocnemys expansa ; it is bent 

 or curved in the Chehnes. To what extent the postfrontal (12) was continued backwards, 

 whether so, as with the parietal, to roof over the temporal fossa, as in the Podocnemys 

 ewpansa,* or, in a less degree, leaving that fossa open superiorly, as in the Emydians 

 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 

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

 which has been preserved, 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. 1 with fig. 14, the suture between g and It.) 

 With respect to the parietal bones (7), 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 strongly 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 (T. XXIX, figs. 1, 2) to the family Paludinosa, it is reasonable to conjecture that 

 it may have appertained to some one of the large Emydians, which we already know 

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



* See Cuvier, loc. cit., pi. xi, fig. 1 a. 



