COLOSSOCHELYS ATLAS. 363 



The commuiiication opened with a reference to the reptilian 

 forms discovered in the fossil state, among which colossal 

 •representatives have been found of all the known tribes, such 

 as the Iguanodon, Megalosaurus, LabyrintJiodon, &c., besides 

 numerous forms of which no living analogues exist, such as 

 the Enaliosaurian reptiles and Pterodadyles. Wo fossil Tes- 

 tudinata remarkable either for size or deviation from existing 

 forms have hitherto been found in the fossil state. The 

 ColossocJielys suppHes the blank in the first respect, whUe it 

 differs so little from the land-tortoises in the general con- 

 struction of its osseous frame, as hardly to constitute more 

 than a sub-genus of Testudo. 



The plastron or sternal portion of the shell affords the 

 chief distinctive character. The episternal portion in the 

 adult is six and a half inches thick, and contracted into a 

 diameter of eight inches, bifid at the apex, and supplied with 

 a thick cuneiform keel on its inferior surface ; this keel con- 

 stitutes one of the principal features in the fossil. The 

 entostemal portion exhibits exactly the form of Testudo, the 

 same being the case with the xiphostemal or posterior por- 

 tion. The plastron in the adult animal was estimated to be 

 nine feet four inches long. (See Plates XXX. and XXXI.) 



The carapace or buckler of the shell coincides exactly with 

 the general form of the large land-tortoises, of which it 

 exhibits only a magnified representation, flattened at the toj) 

 and vertical at the sides, with the same outline and recurved 

 margin. The shell was estimated to have been twelve feet 

 three inches long, eight feet in diameter, and six feet high. 

 The head was estimated to have been two feet long, and the 

 whole animal upwards of 20 feet. 



The extremities were described as constructed exactly as 

 in the land-tortoises, in which the form of the femur and 

 humerus is marked by peculiar characters. These bones in 

 the fossil were of a huge size, corresponding to the dimen- 

 sions of the shell. The ungual bones indicated a foot as 



> On a slip of paper Dr. Falconer I the Testudo elepliantopus, in the College 

 draws the following comparison between | of Surgeons, and the Colossochelys Atlas. 



Test, eleph. Coloss. Atlas. 



From the episternal to end of entostemal 10 inches 2 feet 11 inches 



Length of plastron . . . . 32 „ 9 „ -1 „ 



Length of carapace . . . . 42 „ 12 „ 3 „ 



Ditto along the curve . . . . 54 „ 15 „ 9 „ 



The following calculation is then made as to the total length of the Colossochelys : 



Feet In. 



Length of carapace 12 3 



„ neck 6 



„ head 2 



,: tail 2 



Total . . . 22 3 



[Ed.] 



