Reptiles and Amphibians of Illinois. 217 



seven species are very abundant in these streams within our 

 limits; beyond this number the more exclusively aquatic species 

 are rather scarce, or else only locally abundant. 



The turtles are timid, inofEensive animals, avoiding man 

 whenever possible, and only when cornered exhibiting the 

 strength and quickness which might render them formidable 

 antagonists if they were so disposed. The snapping turtles 

 with their strength and vigor are quite able to hold their own 

 against most enemies. Our species vary in length from about 

 four inches to as many feet, and from one to a hundred 

 pounds in weight. Their food consists ordinarily of fishes, 

 frogs, mollusks, crayfishes, aquatic insects, and vegetation, some 

 being exclusively carnivorous, others taking both animal and 

 vegetable food. None of our species depend entirely upon 

 vegetable food. Several species trouble fishermen at times 

 by devouring fishes which have been caught on trot lines 

 or in set nets. Excepting the Trionychidae, they are not rapid 

 swimmers, and the predaceous species probably get most 

 of their prey by lying in wait for it. An animal once within 

 reach of their jaws must be very c[uick to escape capture. I 

 have occasionally seen an individual making off with a partly 

 devoured water snake. They emit no sounds except by snap- 

 ping the jaws when angered, and a low hiss produced by the 

 sudden compression of the lungs and consequent rush of air 

 through the glottis, when the head and limbs are withdrawn 

 into the shell. The eggs are white, spherical or elongate 

 oval (in the latter case the two ends alike in diameter), and are 

 provided with a rather tough shell. As far as known our 

 species all bury their eggs in sand or earth and leave them to 

 hatch by the sun's heat. 



SYNOPSIS OF THE FAMILIES REPRESENTED IN ILLINOIS. 



Plastron with twelve plates, with no, or but one, transverse 

 hinge. Bridge between plastron and carapace, when pres- 

 ent, formed by wings of the pectoral and abdominal plates. 

 No gular barbels Emydid^. 



