Mr. BELL on two new 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 Testudinide, yet this is so much modified as to 
show a marked approach to the flattened, palmated conformation 
of those of the Emydide, whilst the claws are observed to assume 
somewhat of the length and sharpness which characterize the 
Freshwater family. 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withdrawn within the shell; or, by relaxing the muscles which 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 hinge 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. 
SE2 Some 
