68 TORTOISES AND TURTLES. 



herons are in the habit of nesting, owing to the quantity of insects, snails, worms, 

 and fragments of fish to be met with in such localities ; and they are frequently 

 found in woods where the ground is either moist or swampy. At times 

 they will, however, enter the water of their own free will ; and they have been 

 seen half-buried under loose earth or moss in search of worms and insects. 

 Unlike most members of the family, the box-tortoises shun the light, and are most 

 active during the evening and night, shutting themselves closely up in their shells 

 when the sun is shining brightly. The closure of the shell is also effected at the 

 approach of any large animal ; and when thus securely boxed up, there are but 

 few creatures these tortoises need fear. Like most other terrestrial tortoises, the 

 females lay their eggs in holes dug in the ground by themselves ; the number laid 

 being usually only live or six, whether the parents be half -grown or adult. Each 

 individual egg is carefully covered with earth ; the time taken before the young 

 are hatched being said to vary from eighty -eight to a hundred days. When first 

 hatched, the young are well developed, and of great relative size and strength ; 

 although their shells are still soft and cartilaginous, and the remnant of the yolk- 

 sac depends from the plastron. In Pennsylvania both young and old bury them- 

 selves 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 deeply, are, however, frozen to death during the winter 

 slumber. On account of the strong and disagreeable flavour 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: 



Pond-Tortoises. . z ° 



carapace 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 ligament, 

 while the plastron itself is more or less distinctly divided by a ligamentous 

 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. orbi- 

 cularis), and a nearly allied North American species. The former, which is 

 familiar to most visitors to Southern Europe, is characterised 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 colour, 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 



