66 FOSSIL REPTILIA OF THE LONDON CLAY. 



The fine example of Platemys Bullockii, here described and figured, was purchased 

 for the British Museum at the sale of Mr. Bullock's collection. 



I am happy in the opportunity of expressing my acknowledgments to Charles 

 Konig, K.H., F.R.S., for the urbanity with which every requisite facility was afforded. 



Platemys Bowerbankii. Oiven. Tab. XXIII. 



Report on British Fossil Reptiles, Trans. British Association, 1841, p. 163. 



This species is represented by a fine specimen exhibiting not only the plastron 

 (fig. 2), but likewise a great portion of the carapace (fig. 1), from Sheppy, in the rich 

 collection of the fossil remains from that island in the possession of J. S. Bowerbank, 

 Esq., F.R.S. It equals in size the Platemys Bullockii, in the British Museum, but 

 differs in the absence of the finely punctate character of the exterior surface of the 

 bones ; in the greater antero-posterior extent of the lateral walls, and the longer curves 

 which they form in extending from the body of the plastron. 



The carapace (fig. 1) presents the same equality of breadth of the neural plates 

 (s2 — S/) as in the Emys testudiniformis ; but they diminish more rapidly in length as 

 they recede in position ; and the whole carapace is much more depressed ; it is flat 

 along its middle tract. The sixth neural plate (se) is a hexagon of nearly equal sides ; 

 the seventh (s-) is a pentagon ; the mesial or vertebral ends of the seventh pair of 

 costal plates (jo/7) meet and unite behind it, so as to conceal or supersede the eighth 

 neural plate. In the circumstance of the neural plates decreasing in length without 

 losing breadth, as well as in the mutual junction of the seventh costal plates, the 

 present fossil resembles the Sheppy carapace from Mr. Crow's collection, which Cuvier 

 has figured, and which may, therefore, have belonged to the present species of Platemys. 



The plastron (fig. 2) is thirteen inches in length and ten inches in breadth ; it is 

 rather broader before than behind, rounded at the anterior border, with a shallow 

 emargination at the middle of the posterior border, but wider than in the Platemys 

 Bullockii, and with the angles on each side rounded off. The under surface is nearly 

 flat, slightly convex at the fore part, and as slightly concave behind. The lateral 

 walls uniting the plastron to the carapace are five inches in antero-posterior extent. 



The entosternal (s) resembles that of the Platemys Bullockii in general form, but is 

 longer than it is broad, instead of the reverse proportions. The two anterior sides 

 meet at a right angle. The episternals (es) are broadest behind. The middle part of 

 the plastron is almost equally divided between the hyosternals (/is) and hyposternals 

 (ps). There is a trace of the intercalary piece {hp), which is seen extending across the 

 plastron of the Platemys Bullockii ; here it is wedged into the outer interspace of those 

 bones, like one of the external portions of the composite abdominal ribs in the 

 Plesiosaur. In the relative length of the lateral walls the Platemys depressa most 

 resembles the present species. 



