FOSSIL REPTILES OF DORSET. 5 



posterior more uniformly covered ; also in the sides of the terminal 

 notch being concave instead of convex, as in PL concinnum. There 

 are also divergences in the impressions of the dividing lines of the 

 scutes. The posterior and anterior borders of the carapace are 

 emarginate. The length is twenty-one inches nine lines, breadth 

 twenty inches. 



PLEUROSTERNON OVATUM, Oicen. 



The carapace of this species is elliptical, and rather more 

 pointed behind than before. It has eleven neural plates, including 

 the pygal plate ; the number of marginal plates is eleven on each 

 side. It resembles PL concinnum in the absence of the anterior 

 emargination of the carapace, which characterises PL emarginatum. 

 The length of the carapace, which is very slightly convex, and the 

 margin a little raised, is nineteen inches six lines ; its breadth 

 fourteen inches six lines. 



PLEUROSTERNON LATISCUTATUM, Owen. 



This species differs from the preceding three, by its distinct 

 nuchal and small relative size of the first vertebral scute, 

 the greater relative size of the three succeeding vertebral scutes, 

 and the boundary lines being proportionately deeper than in 

 any other species of Pleurosternon. The outer surface of the 

 carapace is minutely punctuated and rugose except near the borders 

 of the several pieces, where are coarse parallel striae, directed at 

 right angles to the borders. 



GENUS TRETOSTERNON, Owen. 

 TRETOSTERNON PUNCTATUM, Owen ; (Trionyx Balceivelli, 



Mantell.) 



This Turtle was referred by Dr. Mantell to the Trionycidae from 

 an individual found in the Wealden-beds of Tilgate Forest, Sussex. 

 Sir Richard Owen explained in his Report on the British Fossil 

 Reptiles, read before the British Association in 1851, it could not be 

 so referred on account of the absence of the characteristic tooth- 

 like projection, the union of the carapace and plastron by their 

 borders, and the complete ossification of the carapace, which 



