ON BRITISH FOSSIL REPTILES. 179 



Chelone suheristata, nob. — This species, also from the Isle of Sheppey, has 

 the usual thalassian form of carapace, which is narrow, ovate, and contracted 

 to a point behind, with a sternum resembling also existing Chelones, in the 

 form and degree of ossification of its constituent pieces, and the slenderness 

 of the xiphisternals. It may be distinguished from the Chelone breviceps by 

 the smoothness of its carapace, the different form of the vertebral plates, and 

 the development of a sharp ridge on the sixth and eighth vertebral plates. 



The sole example of this species which has come under my observation is 

 the osseous buckler, 9 inches in length and 6^ inches in breadth, in the 

 museum of Mr. Bowerbank. 



Chelone latiscu^ta, nob. — This species is founded on a nearly complete ' 

 buckler of a turtle from Sheppey, measuring 3 inches in length, from the 

 second to the seventh plate inclusive : it may be a variety, or the immature 

 state of Chelone longiceps, but I have not yet had the opportunity of ascer- 

 taining to what extent the relative breadth of the vertebral scutes varies in 

 individuals of different age of existing species of turtle. In the present case 

 the vertebral scutes are nearly twice as broad in proportion to their length, 

 as they are in the Clielone longiceps, or in any of the other well-marked spe- 

 cies of Eocene turtles. 



The indications of Chelonites from Eocene strata, in the works of Parkin- 

 son, Woodward and Konig, being unaccompanied by the anatomical deduc- 

 tions essential to the establishment of their true affinities, have been either 

 misinterpreted or neglected ; and except the citation of Woodward's Chelone 

 Harvicensis, in M. H. v. Meyer's Compilation*, the existence in the London 

 clay of fossil Emydes alone has been recognized in the latest summaries of 

 the present branch of Paleontology f. These, therefore, could indicate but 

 little difference between the present fauna and that of the Eocene period in 

 regard to the Chelonian order. But the case assumes a very different aspect 

 when we arrive at the conviction that the majority of Sheppey Chelonites be- 

 long to the marine genus Chelone, and reflect that the number of extinct 

 Eocene turtles from that limited locality very nearly equals that of all the 

 well-determined species of Chelone now known to exist. For notwithstand- 

 ing the assiduous search of the naturalist-collector, and the attractions which 

 the shell and flesh of turtles offer to the commercial voyager, the tropical 

 seas, though so often traversed, have not as yet yielded more than five good 

 species of Chelone ; and of these only two, as Chelone mydas and Chelone 

 caretta, are known to frequent the same locality. Now, whilst it is obvious 

 that but a small proportion of the organized treasures of the vast deposit of 

 petrified mud and clay which fills the London Basin have been brought to 

 light, the results of the examination of fossil Chelonites evidently show that 

 the ancient ocean of the Eocene epoch was more abundantly provided with 

 turtles, and that these presented a greater variety of specific modifications 

 than the same extent of ocean in any of the warmer parts of the earth at the 

 present day. 



The indications which the Sheppey turtles give, in conjunction with the 

 other organic remams from the same depository, of the higher temperature 

 that prevailed in the latitude in which they lived, cannot be overlooked ; yet 

 at the same time the conditions, which allow of the attainment of the size 

 which tlie present tropical turtles often exhibit, would seem not to have been 

 present in the time and place of existence of the extinct species of Chelone 



* I'alaiologica, p. 104. 



t See Cuvier, Ossem. Fossiles, ed. 183G, 8vo, torn. k. p. 464 ; Bucklawl, Bridgewater 

 Treatise, vol. i. p. 258 ; the recent comprehensive work on Erpetolog)', by :MM. Dumeril 

 and Bibron, torn. ii. p. 533; and Dr. Grant in the British Annual for 1839, p. 266. 



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