Draw the tortoise seen from the side or above, with its shell closed, showing the arrangement of the plates.
Fig. 270.—Reptilian Viscera (lizard).
lr, windpipe; h, heart; lu, lungs; lr, liver; ma, stomach; dd, md, intestines; hb, bladder.
Place soft or tender vegetable food, lettuce, mushroom, roots, berries, and water, also meat, in reach of the turtle. What does it prefer? How does it eat? It has no lips; how does it drink?
Study the movements of its eyeballs and eyelids, and the respiratory and other movements already mentioned. State a reason for thinking that no species of land animals exists that lacks the simple power of righting itself when turned on its back.
Tortoise, Turtle, Terrapin.—The turtles belong to the order of reptiles called chelonians. No one can have any difficulty in knowing a member of this order. The subdivision of the order into families is not so easy, however, and the popular attempts to classify chelonians as turtles, tortoises, and terrapins have not been entirely successful. Species with a vaulted shell and imperfectly webbed toes and strictly terrestrial habits are called tortoises. Species with flattened shells and strictly aquatic habits should be called terrapins (e.g. mud terrapin). They have three instead of two joints in the middle toe of each foot. The term turtle may be applied to species which are partly terrestrial and partly aquatic (e.g. snapping turtle (Fig. [271])). Usage, however, is by no means uniform.
Fig. 271.—Snapping Turtle (Chelydra serpentina).
Most reptiles eat animal food; green terrapins and some land tortoises eat vegetable food. Would you judge that carnivorous chelonians catch very active prey?
The fierce snapping turtle, found in ponds and streams, sometimes has a body three feet long. Its head and tail are very large and cannot be withdrawn into the shell. It is carnivorous and has great strength of jaw. It has been known to snap a large stick in two. The box tortoise is yellowish brown with blotches of yellow, and like its close kinsman, the pond turtle of Europe (Fig. [266]), withdraws itself and closes its shell completely. Both lids of the plastron are movable, a peculiarity belonging to these two species. The giant tortoise of the Galapagos Islands, according to Lyddeker, can trot cheerfully along with three full-grown men on its back. “Tortoise shell” used for combs and other articles is obtained from the overlapping scales of the hawkbill turtle, common in the West Indies. The diamond-back terrapin, found along the Atlantic Coast from Massachusetts to Texas, is prized for making soup.