Mr. Bell on tzco nezo Genera of Land Tortoises. 393 



sequently, that in accordance with this structure, its movements 

 are by far more active than those of any other Land Tortoise I 

 have seen ; and that although the feet retain the clavated form 

 belonging to the Testudinida, yet this is so much modified as to 

 show a marked approach to the flattened, palmated conformation 

 of those of the Emydida, whilst the claws are observed to assume 

 somewhat of the length and sharpness which characterize the 

 Freshwater familj^ These evident affinities to the latter group 

 are remarkably strengthened by a peculiarity of structure in the 

 dorsum or upper bony shell, which is divided into two portions, 

 the posterior of which is moveable, and capable of being brought 

 into actual contact with the posterior margin of the sternum, so 

 as completely to protect the hinder feet and tail when they are 

 withdrawn within the shell ; or, by relaxing the muscles which 

 had thus closed the box, to allow of its being opened to the ex- 

 tent of from one-half to three-fourths of an inch. This singular 

 capability of motion is produced by the absence of any bony 

 union between the fifth and sixth ribs, which are only connected 

 by means of an elastic ligamentous substance. I have since 

 become possessed of several shells of this species, in all the older 

 specimens of which, that part of the inferior margin of the upper 

 shell which is opposed to the edge of the sternum, is actually 

 eroded by the force with which it has been continually brought 

 into contact with it. 



Although the situation of the hinoe I have described, and the 

 part to which the office is assigned of closing the shell, are dif- 

 ferent in the two groups, there is still, in the fact of a peculiar 

 structure being formed for this specific purpose, a relation be- 

 tween them, which, conjointly with the other affinities of con- 

 formation to which I have alluded, appear to me to justify the 

 view I have taken of them, as forming the two links by which the 

 families are connected. 



3 E 2 Some 



