Fig. 92.–Trionyx ferox (American Soft-shelled Turtle). × ⅒.
In the month of May the females seek sandy places along the banks of the waters they inhabit to lay their eggs, generally about sixty in number; and it is remarkable that, though their motions are slow and difficult on dry land, yet at this season they sometimes mount hillocks several feet high. The flesh affords the most delicate food, surpassing that even of the Green Turtle. The geographical distribution is interesting. It inhabits the Savannah as well as all those rivers that empty into the northern borders of the Gulf of Mexico; it ascends up the broad Mississippi, and is found in all its tributaries, even to the very foot of the Rocky Mountains; it abounds in the chain of great northern lakes both above and below the Falls of Niagara, and is common in the Mohawk, a tributary of the Hudson river; but it is not found in any other Atlantic stream between that and the Savannah river, a distance of nearly 800 miles."
T. triunguis, the only African species, ranging from the Senegal and Congo into the Nile-system, but occurring also in Syria, is perhaps the largest of all Trionychidae, reaching a shell-length of almost 3 feet. The adults are olive-brownish above, the throat and under parts of the shell with round, white spots separated by a dark network. The young have whitish specks and spots.
Fig. 93.–Trionyx gangeticus (young). × ⅓.
T. gangeticus and T. hurum are the principal Indian species. The former is the larger of the two, with a shell of more than 2 feet in length; olive above, the young with fine black vermiculations; head with a black longitudinal streak from between the eyes to the nape, intersected by two or three chevron-shaped black streaks; under parts yellowish. T. hurum is olive brown above and below, in younger specimens with conspicuous, large, yellow spots on the sides of the head. The young are ornamented with two or three pairs of large round spots on the back, and the same applies to the beautiful young of the Burmese, T. formosa.
Fig. 94.–Trionyx formosa (young). × 1.
The three genera, Cycloderma and Cyclanorbis of Tropical Africa, and Emyda of India, have a pair of cutaneous femoral valves or flaps on the plastron, beneath which the hind-limbs are withdrawn.