The carapace is rough. The horny shields become very thin with age. The anterior margin of the small nuchal and the neighbouring marginals is faintly serrated. The posterior marginals form slight notches or indentations between their edges. The plastron is almost square behind. The edges of the jaws are nearly smooth, without hook and receiving-notch. The tail is short.
Fig. 77.–Chrysemys concinna, in its third summer, × 1.
Fig. 78.–Chrysemys concinna, in its third summer, × 1.
This species inhabits the South-Eastern States of North America, from Missouri and North Carolina to the Gulf of Mexico. Very large female specimens have a shell sixteen inches in length. The eggs measure from 33 by 25 to 39 by 25 mm. or about 1½ inch in the long diameter.
Emys.–The plastron is movably united to the carapace by ligament, and in the adult has a slightly flexible hinge across the middle, between the hyo- and hypo-plastral plates and the pectoral and abdominal shields. The plastron is large, but does not quite close the box. Besides the small nuchal there are twelve pairs of marginal shields. The head is covered with smooth skin; the temporal arch is complete. The limbs are extensively webbed. The tail of the very young is nearly as long as the shell, but it becomes relatively shorter with age, being reduced in the males to about two-thirds, in the females to half the length of the shell. Only two species are found in Europe, the other, E. blandingi, in Canada and north-eastern U.S.A.
E. orbicularis s. europaea s. lutaria, the European Pond-tortoise.–The shape and coloration of the shell change likewise much with age. In the very young the shell is round, and the shields are rough and slightly keeled, uniform dark brown above, black below, with a yellow spot on each marginal and plastral shield. When half grown the dorsal shields become quite smooth, and are striated or spotted, with yellow upon a dark ground. The head, limbs, and tail are dark, with yellow or light brown spots and small dots. In very old specimens all these yellow marks disappear on the shell, which then becomes uniform brown or almost black. The coloration is subject to much local and individual variation, and there are two main types, the spotted and the radiate. It is difficult to say which of the two is the prettier. One male which I caught in the Alemtejo was very beautiful. The shell was almost black with a greenish shine when in the water, and had many bright yellow and whitish spots. In the radiate type the yellow is sometimes preponderant, so that each shield becomes a study of delicately painted yellow, brown, and blackish lines radiating from the centre. This variety seems to prevail in the south of Spain, decidedly so in the Marismas, also in Northern Italy, whence most of the European markets are supplied. The largest shell in the British Museum is 19 cm. = 7½ inches long. Fischer Sigwart received one from Naples which was about 9 inches long, and this seems to have been kept as a pet, since its shell had been gilt. Specimens about 5 inches in length may be considered as fully adult. There are very few reliable observations on the growth of individuals. One of F. Sigwart's grew in eleven years only about 2.5 cm. = 1 inch, when its shell was 13.4 cm. = 5¼ inches long–total weight of the tortoise 491 grammes, about 1 lb. One of my own grew from 11 to 13.2 cm. shell-length, and 8.3 to 10.6 cm. in width within eight years, but this was one of the specimens which, living in a greenhouse, did not hibernate. This European pond-tortoise is now restricted to Southern and Middle Europe, extending eastwards towards St. Petersburg and into Asia Minor, southwards into Algeria. Formerly it had a much wider range, having been found in post-glacial deposits in Southern Sweden, Denmark, the Netherlands, and in East Anglia. Specimens have been found in the peat of the fens of Norfolk and Cambridgeshire, contemporary with bones of the Beaver, Roe-deer, and Pelican. The same applies to North Germany, where its gradual disappearance from the western and central parts is obvious. Except in Central France it is now practically unknown to the west of the Elbe river. The country between the Elbe and Oder is now debatable ground, Emys being exceedingly rare. Some fifty years ago this seems to have been different, to judge from the fact that farmers were rather fond of keeping a tortoise in the water-troughs of the cattle to keep the water free from worms and other impurities. Hence arose a silly superstitious custom. It was considered equally conducive to the health of the pigs to keep a tortoise in the foul tub into which all the dish-water and kitchen-refuse–as potato-peels, sour milk, etc.,–were collected before the mess was given to the pigs.
A specimen is still occasionally caught in the Havel and Spree rivers. I myself have heard of one or two in the backwaters of the Oder near Frankfurt, but they are vanishing, and it is difficult to say exactly why. The universal lowering of the water-level owing to better drainage cannot quite account for it, since there are thousands of suitable ponds, swamps, and backwaters left. In Poland and in Eastern Prussia the tortoise is still common.
This creature lives on a strictly animal diet. Worms, insects, frogs, fishes form its main sustenance. Fishes are regularly stalked. The tortoise watches its opportunity, slowly it half crawls, half swims along the bottom, rises imperceptibly by a few gentle movements of the widely spread-out webbed feet, then opens its sharp cutting jaws wide, and makes a grab at the belly of the fish. Frogs are most easily stalked when they sit upon a floating leaf. The tortoise rises from below, and often waits with the nostrils and eyes just above the water and close to the frog. After a while it sinks, and rises again, this time actually touching the toes of the non-suspecting frog, smelling at them and deliberately biting with a sideward turn of the head.