155 



SECTION 11. 



THE 



FOSSIL REPTILIA OF THE CEETACEOUS FORMATIONS. 



Chapter I.— Order CHELONIA. 

 Genus, Chelone, (Turtles.) 



The Cretaceous formations of England consist of the " Upper Chalk," which is 

 white, and is commonly characterised by having horizontal layers of flint nodules ; of 

 the " Middle Chalk," which is as white as the Upper Chalk, but usually without the 

 flints in regular layers ; and of the " Lower Chalk," which when wet, and sometimes 

 also when dry, has a gray tinge. These divisions of the chalk deposits, which in 

 some parts of the south-east of England attain a thickness of one thousand feet, 

 are best distinguished by some of their organic contents, as e. g. the Terehratulida, 

 the EcMnidcB, and the Venfriculidce* Beneath the Chalk there is a series of Sands 

 and Clays, which in England have received the name of " Upper Green-sand," " Gault," 

 and " Lower Green-sand." The present Section of this History will be devoted to the 

 description of the remains of the Fossil Reptilia that have come under the notice of 

 the author from any of the above-named divisions of the Cretaceous Period. 



One of the earhest, if not the first, indication of the occurrence of fossil 

 Turtles in the formations of the Cretaceous Period, is given by the celebrated 

 anatomist Camper, in a ' Memoir on the Petrifactions found in St. Peter's Mount, 

 Maestrichtj't where, referring to some specimens which he had procured for the 

 British Museum, he writes : — " Another very beautiful specimen, a foot and a half 

 long, and about ten inches broad, I have been induced to add, because it contains the 

 anterior part of the scutum of a very large Turtle. Of this Mr. John Hunter has 

 an analogous bone from the same mountain in his valuable collection, but sent to him 

 under another name. I am convinced it belonged formerly to a Turtle ; — first, because 

 I have from the same mountain the entire back of a Turtle, four feet long and sixteen 

 inches broad, a little damaged at the sides, and a pretty large fragment of another 

 Turtle in my possession : secondly, because I have a similar one, but so placed 

 within the matrix, as to show the inside of that piece in the back of a large Turtle I 

 got in London, by the favour of Mr. Sheldon : thirdly, because I have amongst these 

 bones the lower jaw-bone of a very large Turtle, of which the crura, though not 

 entire, are seven inches long, and distant from one another six inches ; the thickness 

 is equal to one inch and a quarter."^ In a collection of engravings belonging to my 



* See an excellent Paper, "On the different Beds of the White Chalk," by J. Toulmin Smith, Esq., in 

 the ' Annals of Natural History ' for November, 1847. 



t Philosophical Transactions, 1/86. | Ibid., p. 450. 



