452 LOWER VERTEBRATES. 



The genus is well represented in Europe by the yellow-tortoise, C europasa, inhabiting 

 all the wanner countries, where they are to a limited extent used for food. 



The family Chelydkidje is represented in the New World, from Canada to 

 Ecuador, by the common snapping-turtle, Cheh/dra setpentina, an animal adapted for 

 active defence. The shield being too small for the complete retraction of the extremi- 

 ties, the enemy is boldly faced and attacked, the reptile's long reach and strong 

 jaws being suiEcient to defeat the attacks of any ordinary foe. The elongated tail of 

 this animal is very characteristic, and from its appearance has not only given rise to 

 tlie popular name, ' alligator-turtle,' but, appended to the small, comparatively thin shell, 

 gives an elongated apjiearance to the body, resulting in the specific name, serpeutma, 

 In its habits, both in the water and on land, the snapping-turtle is bold and fierce, and 

 will often suffer itself to be lifted from the ground by the object which it has grasped 

 rather than let go its hold. As it elevates itself for the attack, with half-open mouth 

 and sullen eyes, there is something fierce and defiant in its attitude, though it is so 

 slow and awkward in recovering itself after missing its jioint of attack that it pre- 

 sents a most ludicrous picture. Members of the species are remarkably strong — the 

 elder Agassiz states that he has observed one to bite off a piece of plank more than 

 an inch thick — and they grow to a considerable size, being our largest inland repre- 

 sentative of the order, specimens not infrequently exceeding the length of three feet. 

 In the northern states, from the tenth to the twentieth of June, the female, at early 

 morning, leaves the water and crawls to a sand bank, digs a small cavity, not with its 

 tail (a popular belief), but with its hind leg, into which the small spherical eggs are 

 deposited to the number of twenty-five or thirty, when the sand is drawn over them, 

 the surface smoothed down, and the animal is soon back in the water, the entire ope- 

 ration not lasting over twenty minutes. This mode of oviposition is different from 

 that of our other turtles. While the snapper is satisfied with nothing but sand, the 

 painted and speckled-tortoises put up with any soil in which they can scrape, not a 

 cavity, but a hollow, and .at evening rather than early morning. An allied form, 3fa- 

 crochelys lacertina, inhabits the tributaries of the Mexican Gulf, extending north- 

 ward in the Mississippi as far as Missouri. Its diet, like that of the previous species, 

 consists of the smaller animals, which it captures by a quick lunge, seizing them in its 

 powerful jaws. 



The family Cinosternid^ includes the smaller fresh-water turtles, the largest of 

 which is smaller than the smallest of the Chelydridje. On leaving the w.ater they 

 seldom attempt any long journey, but bask in the sun in such a situation that on the 

 slightest sign of danger they can drop into their native element, though, if so unfor- 

 tunate as to be cajitured, they, though ridiculously small, endeavor to defend 

 themselves by freely using their jaws. They are carnivorous, and possibly, to some 

 extent, herbivorous. The eggs are few in number, and, unlike other turtles, excepting 

 the TrionychidiB, are covered with a strong glazed shell, which, though thick, is very 

 brittle. 



Aromochelys odomta is a small turtle found in pools, often covered with a thick 

 growth of green algre, inhabiting the more eastern portions of the United States, 

 and known as the musk-turtle, besides other savory names, of which the scientific 

 is perhaps the most expressive. In length the shell of this animal seldom reaches six 

 inches, while the plastron is cruciform, resembling to some extent that of Chelydra 

 serpentina. The convex brown carapax, generally covered with algae, the pointed head 

 and strong odor, renders this animal not easily confounded with our other turtles. 



