402 CHELONLANS. 



SECOND FAMILY. Emydoida, (Gr. sptg, emus, a fresh-water 



tortoise.) 



This is a most numerous family, including a large number of 

 well known species, which present great varieties of habit, size, 

 and structure. Dumeril and Bibron unite the Emydoida and 

 Chetyoida into one family, under the name of ELODITES, refer, 

 ring the Emydoidce to the division Cryptodera, and the Clielyoida 

 to the division Pleurodera. Our limits do not allow us to detail 

 minutely the distinctive peculiarities of this family, or to assign 

 at large the differences existing in the various sub-divisions un- 

 der which it is exhibited. 



In these Tortoises, the box in which the animal is enclosed, is 

 less thick and strong than in the Land Tortoises, not becoming 

 completely ossified until late in life; its figure is oval, for the 

 most part, broader behind than before. All the bony plates show 

 great constancy and regularity of arrangement. The outside of 

 the whole shield is covered with scales, as is, more or less, the 

 skin of the head, neck, limbs, and tail; the tympanum is visible, 

 and the eyelids are of equal height. 



Nearly the whole of these are eminently MARSH TORTOISES. 

 Almost all of them can withdraw and conceal their limbs within 

 the carapace and plastron ; but in the Platysternvn, (Gr. broad- 

 sternon,) the plastron or sternon from its width, suffices to con- 

 ceal the limbs when folded ; yet the head remains constantly 

 exposed. The food of these Tortoises is both vegetable and 

 animal. None of them catch active prey, or are in any way 

 ferocious; when hard pressed, however, they defend themselves 

 by biting. They lay their eggs on dry land, in holes which they 

 dig with their hind legs; the land species, from two or three to 

 five or seven ; the water species, from ten or fifteen to twenty, 

 thirty, or even more. (Agassiz.) The shell of the eggs is never 

 brittle, but rather flexible, and less calcareous than in some other 

 families. 



The genera Emys and Cistudo, are prominent representatives 

 of this family. In the Emys, the fore feet have five toes; the 

 hind feet, four; the plastron is broad, immovable, solidly united 

 to the carapace, and covered with twelve plates; the head is 

 about the ordinary size ; the tail long. 



Emys Muhlenbergii, or Muhlenburg's Tortoise, is the smallest 

 known species, about four inches in length ; found in New Jer- 

 sey and the eastern part of Pennsylvania. 



E. rugosa, (Lat. wrinkled,) or E. rubriventris, (Lat. red- 



