THE TURTLE. 207 



the acetabulum horizontally, toward the median line, is 

 the ischium. 



8. The anterior of the two horizontal bones is the pubis. 



Between ischium and pubis is a large hole, the obturator 

 foramen. Ischia and pubes of opposite sides meet in a 

 median ventral symphysis. 



In both fore and hind legs find the parts already found 

 in the legs of the frog, observing the separation of the 

 two bones of the forearm and the two of the shank, and 

 the shortness of the tar sal bones. 



Development. The eggs of certain species of turtles 

 (the eggs which are perhaps most easily found) are laid 

 in early summer in sunny sandbars in rivers, lakes, and 

 creeks. At night the mother ' turtle digs down into the 

 sand, and hides away her eggs a foot or more beneath the 

 surface, smooths the sand above them, and leaves them 

 to be hatched by the warmth of the sand, absorbed from 

 the sun's rays. Although the mother turtle has been 

 careful to remove visible traces of their whereabouts, they 

 may yet be found by very simple means. The disturbed 

 sand in which they lie is much more readily penetrated by 

 a stick than are other places on the bar. Hence, if a stick 

 be pushed into the sand at short intervals along the line 

 of the turtle's tracks, and a place be found where it enters 

 very much more readily than elsewhere, that is the place 

 to look for the "nest." The unmistakable tracks of the 

 turtle across sunny bars of pure sand will seldom be fol- 

 lowed in vain in May or June ; for the turtles do not 

 ordinarily frequent such places. 



The young turtle which hatches from the egg is essen- 

 tially like the adult, except in size. It differs somewhat 

 in having its legs and pectoral and pelvic arches free from 

 the shell. During later development the sHell encroaches 

 upon, and partially incloses, these parts. Young in all 



