318 



PALEONTOLOGY. 



part.* The Chelone longiceps resembled a Trionyx in the 

 shape and production of the muzzle (fig. 91, b), and an 

 Emys in the extent of ossification of the carapace and plas- 

 tron, but retained all the essential characters of a turtle. 



/2 



Fig. 109. 

 Pleurosternon emarginatum (Purbeck). 



The estuary genus Trionyx (soft turtle) is represented by 

 many beautiful species in the upper eocene at Hordwell ;t 

 the fine rugous sculpturing of the outer surface of the 

 carapace and plastron, in this genus, makes the recogni- 

 tion of fossil fragments easy. The fresh-water genera Emys 



* The upper end of the femur from Sheppy, in t. xxix. of Monograph of 

 Fossil Keptilia of the London Clay, Pataontographical Society, 1850, belongs to 

 this species. See also " Hist, of Brit. Foss. Eeptiles," pp. 10-40, pis. 1-22. 



f Op. cit., pp. 50-60, pis. 26-33. 



