THE LAND TORTOISES AND TERRAPINS 2425 



and strength; although their shells are still soft and cartilaginous, and the remnant 

 of the yolk sack depends from the plastron. In Pennsylvania both young and old 

 bury themselves deep in the ground about the middle of October, where they 

 remain till the latter part of April; the spot selected having a dry soil, and being 

 protected from the cutting blasts of the north. Many individuals which have not 

 buried themselves sufficiently deep, are, however, frozen to death during the winter 

 slumber. On account of the strong and disagreeable flavor of their flesh, doubtless 

 engendered by the nature of their food, the box tortoises are not eaten. 



In marked contrast to the vaulted and abruptly-descending carapace 

 e of the box tortoises, is the depressed and shelving shell of the pond 

 tortoises, this difference indicating a distinction in the habits of the two genera. 

 Thus whereas the box tortoises are, as we have seen, mainly land reptiles, the pond 

 tortoises are as decidedly aquatic in their mode of life. In addition to the difference 

 in the form of the shell, the members of the present genus are readily distinguished 

 from those of the last by the beak not being hooked, and by the presence of a bony 

 temporal arch in the skull. In the shell the carapace is united to the plastron solely 

 by a ligament, while the plastron itself is more or less distinctly divided by a liga- 

 mentous transverse hinge, upon which its two lobes are movable. Agreeing with 

 the box tortoises in having the top of the head covered with undivided skin, the pond 

 tortoises differ by having the toes fully webbed, and also by the more elongated tail, 

 which, while very long in the young, is of moderate length in the adult. Although 

 the genus Emys was formerly made to include many of the fresh-water terrapins, it 

 is now restricted to the European pond tortoise (E. orbicularis) , and a nearly-allied 

 North-American species. The former, which is familiar to most visitors to South- 

 ern Europe, is characterized by the short oval form of its carapace, which is widest 

 posteriorly, and in the young state has a more or less distinct median keel. In color, 

 the upper shell of the adult is dark brown or black, ornamented with a variable 

 number of light, usually yellow, dots or radiating streaks, the plastron being either 

 yellow, brown and yellow, or almost wholly blackish brown. In the young, however, 

 the upper shell is dark brown, and the lower black, all the shields of the latter, as well 

 as the marginal ones of the former, having a large yellow spot. The skin of the 

 head, neck, body, and limbs is marked with yellow and black in varying propor- 

 tions, the head of the male having brownish dots on a darker ground, while in the 

 female the dots are yellow. When fully grown, the shell attains a length of seven 

 and one-half inches, but in most of the specimens exported to England it is not 

 much more than half that size. At the present day the pond 'tortoise is found, in 

 suitable localities, in South and East Central Europe, and Southwestern Asia as far 

 as Persia, and in Algeria. During the Pleistocene period, when the climate of 

 Northern Europe must at certain times have been much more genial, the pond tor- 

 toise had a much more extensive distribution, its fossilized remains having been 

 found in the superficial deposits of Belgium, Denmark, Germany, Lombardy, Nor- 

 folk, Sweden, and Switzerland. The American species, which inhabits the North- 

 eastern United States and Canada, has the carapace rather more elongate, and the tail 

 shorter, the former being black with pale yellow or brownish circular spots, and the 

 plastron yellow with a large black patch on each shield. 



