446 LOWER VERTEBRATES. 



sand, and, by probing with a slender stick, finds the exact position of the eggs. Ex- 

 perience has taught him that in just fourteen or fifteen days the turtle will again 

 return to this same locality to deposit, in a new hollow, a second, third, fourth, or 

 even a fifth lot of eggs, and, so, stationing himself on watch, he surprises the unsus- 

 pecting animal as she leaves the water, by means of a pole turns her on her back, and 

 thus leaves her until means are found for carrying her to the crawl. 



If the eggs are not discovered, in about six or eight weeks, incubated by the sun, 

 they hatch, and the young scramble towards the water, on the way to which large 

 numbers are killed by birds, and during the first few weeks of their marine life, their 

 shell being comparatively soft, they are destroyed in large numbers by sharks and 

 other predatory fishes. The flesh of the Pacific form, though at certain seasons of the 

 year unhealthful, is said to rival the Atlantic in flavor. The eggs are in great demand, 

 being of particularly rich flavor and are collected in large numbers by the natives of 

 the East Indies. They are only of about an inch in diameter, and are said to keep 

 fresh for a considerable time. 



In concluding with the Cheloniidaj a singular fact may be mentioned. The logger- 

 head and green-turtles not infrequently interbreed, and the offspring, known to 

 the fishermen as the ' bastard-turtle,' has been described as Colpochelys kempii. 



The family Propleueidje is represented by the extinct genus Osteojihygis, the 

 largest species of whicli are from the cretaceous deposit of New Jersey. The family 

 is interesting in that its representatives have peculiarities of structure which corre- 

 spond on the one hand with the sea-turtles, and on the other with the fresh-water 

 Trionychidfe. 



The family Tbionychidj=; is of particular interest, and is represented by several 

 living as well as fossil forms. The soft-shelled turtles, as the members of this family 

 are called, have the body greatly depressed, sub-circular in outline, and covered with 

 soft skin. The feet are formed for swimming ; the toes distinct, strongly webbed, .and 

 terminated by three claws. They are carnivorous animals and lie in wait, half buried 

 in the mud of the warm, shallow pond-holes which they inhabit, their long neck and 

 head swaying to and fro in the water witli a serpentine motion and occasionally pro- 

 jecting towards the surface, where the elongated nostrils are protruded above, and a 

 fresh sujjply of air is taken in. In ploughing through the mud they often meet with 

 fresh-water mussels, of which they are particularly fond. They are active swimmers 

 and purely aquatic, leaving the water only when compelled to. The eggs, the shells 

 of which are hard and calcareous, are deposited but a few feet on shore, the young 

 easily finding their native element. On the pond in which they live drpng up, 

 retreat is found, in company with eels and siluroid fishes in the underlying mud, 

 where they remain until the period of drought is over. In confinement they are 

 active and aggressive, though they feed readily, eating vegetable as well as animal 

 food. 



Amyda mutica is the smallest of the American Trionychidse and inhabits the 

 valley of the middle and northern tributaries of the Mississippi as well as the St. Law- 

 rence rivers. It is distinguished from the members of the succeeding genus in having 

 no tubercles on the carapax. A large specimen, measuring twelve inches from the 

 front to the hind margin of the shell, contained in its alimentary tract fragments of 

 larval insects. 



As2ndo?iectes ferox was described as early as 1771 and is popularly known as the 

 soft-shelled turtle. Its habitat is more southern than that of the previous form, being 



