Zoological Society. 56 



thickened, and slightly inflexed, and the superior fold of the columella 

 is scarcely distinguishable. 



May 14. — Rev. John Kirby in the Chair. 



The conclusion of the paper by Dr. Falconer and Capain Cautley 

 on the Gigantic Fossil Tortoise of India was read : — 



" On a former meeting we went through the anatomical characters 

 presented by the remains of the Colossochelys Atlas. Commencing 

 with the plastron, we traced the modifications of form through the 

 costal elements of the carapace and the dorsal vertebrae, all of which 

 bear the closest resemblance to the ordinary type of the Chersite Che- 

 lonians, or true land tortoises. A like result followed the examina- 

 tion of the extremities, which, as exhibited in the remains of the 

 humerus, femur and ungueal phalanges, were seen to be constructed 

 exactly on the plan of Testudo, with columnar legs and truncated 

 club-shaped feet, as in the proboscidean Pachydermata. The same 

 direction of affinity was observed throughout the conformation of 

 the head. The only portions of the skeleton from which more or less 

 direct evidence was not derived, were the neck and tail vertebrae, of 

 which there were no specimens in the collection. The general re- 

 sult of the examination showed that the Colossochelys Atlas was 

 strictly a land tortoise in every part of its bony frame ; and the im- 

 pressions of the horny scutes proved the like in regard to the arrange- 

 ment of its dermal integument. 



" The principal distinctive characters were found in the sternum, 

 which is enormously thickened at its anterior extremity, along the 

 united portion of the episternal bones, and contracted into a neu-row 

 neck, so that the width of the combined episternals does not much 

 exceed their thickness : this thickened portion bears on its under side 

 a deep massive cuneiform keel, which terminates upon the commence- 

 ment of the entosternal piece. There is more or less thickening of 

 this part in all the species of Testudo, and the amount of it is very 

 variable in different individuals of the same species ; but there is 

 nothing approaching the same degree of contraction in reference to 

 the thickness, nor aught like a developed keel, in any of the existing 

 land tortoises which we have either had an opportunity of examining, 

 or seen described in systematic works on the tribe. The keel in the 

 fossil is feebly shown in the young animal, but strongly marked in 

 the adult. Conceiving that generic distinctions are only legitimate 

 in the case of well-defined modifications aifecting some of the leading 

 characters in the organization of an animal, we do not consider our- 

 selves warranted in attaching a higher systematic importance to the 

 Colossochelys than as a subgenus of Testudo, which may technically 

 be defined thus (the distinction resting mainly on the form of the 

 sternum) : — 



Subgen. Colossochelys. 



Testa solida, immobilis, sterno antice in collum vald'b incrassatum, 

 subtus carind crassd cuneiformi instrucium, angustato. Testudo 

 terrestris, statural et mole ingenti (inde nomen koXooctos et x^Xvs) 



