88 
GUIDE TO THE 
dom, viz.) that including the Tortoises and Turtles. At 
first sight it would not be suspected that they had any 
structural affinities with the birds surrounding them, but 
so closely are they allied to the feathered division of the 
animal kingdom, that birds and reptiles are now regard¬ 
ed as constituting one great section, viz., the Sauropsidcu 
It would be out of place in a popular notice of the 
animals exhibited in the Gardens, to enter into an ana¬ 
tomical disquisition regarding the structural features 
which distinguish the two classes, Aves and Reptilia. 
The Tortoises and Turtles form a toothless group of 
the reptiles called Chelonia. They approach the group 
Amphibia represented by the Frog, although they are at 
the same time markedly separate from it, and also from 
the ordinary type of vertebrate structure. 
They have only to be looked at, to be seen that they 
are enclosed in an osseous box, or shell, that protects the 
centres of the three vital systems, the circulatory, the 
digestive and the generative, and into this shell the head, 
limbs and tail can be retracted. The box is formed by the 
ribs and a number of the vertebrae of the back, and by 
special bones on the under surface, and it is covered 
either by soft skin or by horny plates. The horny 
plates which cover the shell of one of the marine species 
is the substance so well known as tortoise-shell and which 
is used for making combs and other objects. This species 
abounds in the Indian Ocean and the Bay of Bengal. 
On one occasion, the edible marine Turtle was kept alive 
in a tank in the Garden for three months, but as it found 
no suitable food, it died. Those exhibited in this House 
are all fresh-water species, but some of them are semi¬ 
terrestrial. 
