Illustrating the ample chamber-like space provided within the carapace for the retraction of the head and limbs.
There are several water-tortoises presenting a considerable external resemblance to the forms already noticed which belong to distinct family groups. Thus the Matamata Tortoise of Northern Brazil has at first sight, except for its short tail and nose-like proboscis, much in common with Temminck's snapper. Fimbriated and foliaceous membranous outgrowths are developed on the head and neck to a much more luxuriant degree, and it would be interesting to ascertain if it possesses similar decoy-appendages inside the mouth.
The so-called Snake-necked Water-tortoises of South America, and the Long-necked aquatic ones of Australasia, possess modifications of skull-structure and other details that indicate family distinctness. A broad external character that serves to separate this group from the Terrapins and all preceding forms is that the neck, when drawn within the cavity of the carapace, is not flexed in the form of the letter S, but simply bent sideways along the anterior margin of the body. The species belonging to this group, which includes the Matamata, Snake-necked, and Soft-shelled Water-tortoises, and also a few essentially terrestrial species, are distinguished collectively by the appellation of the "Side-necked" Tortoises.
Turtles.
By permission of the New York Zoological Society.
SNAPPING-TURTLE.
Also known as the Alligator-terrapin, with reference to its long, alligator-like tail.
Certain of the Terrapins, or Water-tortoises, belonging to the groups above described frequent saline river-estuaries and salt marshes, but none are strictly marine. With the Turtle Family, however, we arrive at an exclusively pelagic section, in which the animals are specially adapted for life in the high seas, the walking-limbs of the terrestrial and fresh-water species being replaced by long and powerful swimming-flippers. The shell in these marine Chelonians is more or less heart-shaped and flattened, and the carapace and plastron are always separate, and never united in a rigid box-like form, as with the Land-tortoises. In common with those fresh-water tortoises which pass the greater portion of their existence in lakes or rivers, the Marine Turtles resort to the land to deposit their eggs. The locations chosen are the sand-beaches or isolated sandy islets in tropical oceans, wherein, after excavating hollows to receive them, the eggs are covered up and left to hatch with the heat of the sun. The eggs of turtles differ from those of the Land-tortoises and Terrapins in that their external covering is soft or leathery. So soon as the young turtles are hatched, they emerge from the sand, and instinctively make their way to the water. Many, however, are the perils that beset their course, and few there be out of perhaps 80 or 100 turtlets which gain the shore and get through into deep water. Fish-hawks and sea-birds of every description are waiting ready to pounce down upon them immediately they make their appearance, or to thin their ranks as they run the gauntlet of perhaps 100 yards or so to reach the sea in safety. Even at the waters edge the ordeal is by no means passed. Shoals of the smaller sharks and other predatory fish are continually cruising round in the shallow water, and have as high an appreciation of the toothsomeness of tender turtle as the proverbial London alderman. The writer was fortunate on one occasion, among the coral islands on the Australian coasts, to light upon a young turtle brood just emerging from their sandy nest. The majority were assisted to the sea, and a few, reserved in the interests of science, were liberated in a bath of sea-water to have their first swim. Snapshot photographs were taken, one of which, reproduced on page [561], serves to illustrate the great relative length of the paddle-like limbs at this early stage and the variety of postures assumed during natation.
