]88 BRITISH FOSSIL REPTILES. 



to be met witli in the deposits of a large estuary. I commence tlie description of 

 these Wealden Chelonites by those which indicate a species of the marine family. 



Portions of the carapace and plastron, and bones of the extremities of a large 

 species of Turtle, some of them indicating individuals with a carapace nearly three 

 feet in length, form part of the Mantellian collection, purchased by the Trustees 

 of the British Museum, and now in the Museum of Natural History, Cromwell 

 Road. 



After comparison of these specimens I have come to the conclusion that the 

 Wealden species differ from Chelone imbricata, Chelone carinata, and other recent 

 species, in as great a degree as do most of the Eocene Ghelones, in the greater 

 extent of ossification of the costal interspaces and of the plastron. 



A characteristic portion of the great Wealden Turtle is represented, of the 

 natural size, in Plate 51. It includes the second and third marginal plates, and 

 considerable portions of the first and second costal plates, with the connate 

 portions of the pleurapophyses, or vertebral ribs. These are remarkable for their 

 breadth and prominence, and have suggested the name proposed for the present 

 species. 



In the same plate are represented a mutilated right iliac bone (fig. 3) and the 

 right femur (fig. 2) of, probably, the same species of Turtle. These, also, are 

 from the Wealden formations of Tilgate Forest. 



Figure 4, Plate 52, gives a view of the inner surface of the left hyposternal, 

 half the natural size of, probably, the same species of Chelone. It is embedded in 

 a slab of Wealden stone. 



As compared with existing Turtles, the ossification of the plastron is more, 

 advanced or more extensive, the rays of bone from the outer and inner free borders 

 of the hyposternal being shorter and their interspaces more filled up. A nearer 

 approach is thus made in this Wealden species, as in some of the Eocene Turtles, 

 to what may be regarded as the more general type of the Chelonian carapace. 



Chelone gigas, Owen. Plates XXX, XXXI. 



In the course of the determination and description of the fossil remains 

 referable to the marine genus Chelone (Turtles) fragmentary specimens from 

 the Eocene clay of the Isle of Sheppey indicated the then existence of a species, 

 as shown in fig. 5, Plate 40, much larger than those described in Vol. I, pp. 7 — 44. 

 Recently, however, have been acquired from that locality, for the Palajontological 

 Department of the British Museum of Natural History, remains of this giant of 

 the Family Marina, of which I have selected for illustration the skull, represented 

 in Chelonia, Plate XXX, of the natural size, viewed from above ; other views of 



