SUB-CLASS I. ENOPLIA.

(Mailed Reptiles.)

The Mailed or true Reptiles are principally distinguished by having the body encased in a series of plates of various degrees of hardness, sometimes imbedded, like stones in a pavement, into compact shields, at others forming overlapping scales, and yet again constituting a granular or tuberculous shagreen. In many particulars their anatomical organization is of a higher grade than that of the Amphibia; they have perfect ribs; and the occipital condyle, or joint by which the skull is connected with the spinal column, is single. They are subject to no metamorphosis, but are evolved from the egg in the form of the parents gills (branchia) are never present in any stage, but respiration is performed entirely by means of lungs. The economy of reproduction partakes of the characters of that of Mammalia and Birds, and not that of Fishes; the eggs are always furnished with a calcareous covering, either shelly or coriaceous in texture.

The Enoplia are divided into four Orders, founded on diversities of form, the presence or absence of limbs, and the character of the mailed. covering. These are named Testudinata, Loricata, Sauria, and Ophidia.

ORDER I. TESTUDINATA.

(Tortoises.)

THE appearance of an animal of this Order will naturally recal to the mind the mailed Armadillos among the Edentate Mammalia, as the Sauria will remind us of the Pangolins. The Tortoises are readily distinguished from other Reptiles by their body being inclosed in a double buckler, which admits only of a partial protrusion of the head, tail, and limbs. The bones of the skeleton, though essentially the same as those found in the preceding classes, are strangely modified. If we remove the convex shield, called the carapace, that covers the upper part of a Tortoise, and turn it up, we shall find on the inner surface the vertebral column imbedded into an immovable piece, and the ribs flattened and widened so as to touch each other at their edges. The vertebræ of the neck and of the tail alone are free. The lower plate or plastron, in like manner, is composed of pieces representing the breastbone or sternum, united by sutures.

The external surface of these shields is covered with a series of plates of a horny (or sometimes leathery) texture, of regular but varied forms, united at their edges, but sometimes overlapping posteriorly. The shoulder-blade and all the muscles of the arm and neck, instead of being attached to the exterior of the ribs and spine,

as in other vertebrate animals, are all within, as are also the bones of the pelvis, and even the muscles of the thighs; so that a Tortoise has been described as an animal turned inside out. The

jaws are destitute of teeth, but are invested with horn like those of birds, and form in fact a powerful beak. The head, neck, tail, and limbs, are clothed with a tough skin, in which are imbedded plates, either connected or detached.

The sphere of action of the Testudinata is either the land or the water. Of those which are aquatic, some inhabit marshes, pools, and rivers; others are exclusively marine. The walk of the terrestrial species is slow, even to a proverb; the legs are short, restricted in motion, and being placed at a distance from the centre, they form a sort of short crutches, able to drag the unwieldy

body along, but unable to restore the prone position if the animal be laid on its back. The feet seem like stumps abruptly cut off, armed around the edge with a set of blunt nails, which serve as a sort of grapplings to hold on the surface of the ground and drag the body forwards. To an animal which feeds on herbs, the power of pursuit is useless; nor is it necessary that swiftness in escape should be conferred on one which can draw in its head and limbs on the approach of danger, presenting only a solid case of mail, in which it may defy every enemy but man.

On the other hand, the marine species swim with great rapidity, rushing along beneath the surface like a bird on the wing. The feet take the form of powerful fins, and the form of the body is flattened, and thinned to an edge, both of these provisions facilitating progression through a dense medium. "But the well-developed flipper that enables the Marine Tortoise to oar its way with swiftness, is even a worse organ for land-progression than the clumsy foot of a Land Tortoise. Not but that they will shuffle back to the sea, which they have only occasion to leave in order to deposit their eggs, at a good pace, and they will deal heavy blows with their flippers to those who attempt to stop them, (for they, as well as the Land Tortoises, are very strong,) as those who have been foiled in turning Turtles have known to their cost."

The eggs are of an oval form, and are covered with a white calcareous shell, much resembling those of birds. Those of many of the species are eaten by man.

The food of the Testudinata is various: the

terrestrial species are believed to subsist exclusively on vegetable diet; the marine species add to this the flesh of large shelled mollusks; the marsh and fresh-water kinds prey on fishes, young birds, insects, worms, and any other animals they

can overcome.

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About one hundred and twenty species are known to belong to the Order, of which twentyeight are terrestrial, eighty-four are fluviatile, and eight are marine. They are confined to the warmer regions of the earth; none of them being properly inhabitants of the British Islands; but occasional occurrences of some of the marine species on our shores are recorded, and a terrestrial Tortoise is imported in some numbers from the south of Europe, and kept as a pet in gardens.

We shall consider the Tortoises as comprised in five Families; Testudinida, Emydida, Trionychida, Sphargida, and Cheloniada.

FAMILY I. TESTUDINIDE.

(Land Tortoises.)

In this Family the carapace is very high and convex, solid in structure, and covered with a horny shell. The general form may be illustrated by the common Greek Tortoise (Testudo Græca), familiar to most of our readers. But the principal and most remarkable peculiarity, and that which most perfectly indicates the manner of life common to the group, is the conformation of the limbs the feet are short and stumpy, nearly of equal length, with toes scarcely distinct, immovable,united by a thick skin, and forming a sort

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