LARGE TORTOISES 
It is to be noticed, however, that the skin skeleton 
of the tortoise tribe is not absolutely swi generis. In 
detail, of course, nothing like it is found in any other 
reptile at present known. But the dorsal part of the 
box or carapace is, of course, to be compared with 
the dorsal bony skin shields of crocodiles, while the 
same comparison holds good with regard to the ventral 
plastron, which is, moreover, comparable to the thin 
ossifications found on the ventral surface of Hatteria, 
and in that reptile termed abdominal ribs. Toothless- 
ness happens not to be an attribute of any living group 
of reptiles except the Chelonia ; but there are extinct 
families, though not orders, which are in the same 
way without teeth. Here, as elsewhere in Nature, 
hard and fast lines of demarcation do not exist. The 
selection of tortoises at the Zoo is a considerable one 
at any time. 
TESTUDO DAUDINI 
This tortoise is actually the largest living repre- 
sentative of the giant tortoises of the world. Large 
tortoises do not differ from small ones, such as the 
Testudo greca of southern Europe, and of our streets 
in London at certain times. That is to say, they are 
anatomically not separable, though vastly exceeding 
them in size, and also characterized by a varying 
number of small external and other features, which 
allow us to place the large tortoises in several species. 
At present we only find very large tortoises on small 
islands. It is hardly an exaggeration to say that the 
smaller the island the larger are its tortoises. This is 
very unexpected, because, among the mammalia at 
any rate, beasts seem to require a spacious environ- 
ment to attain to any bulk. Madagascar, for example, 
has small mammals, while in the forests of the neigh- 
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