238 VERTEBRATE ZOOLOGY 



gentle; it is omnivorous. It makes the crudest nest of any of the 

 species that the writer has studied. On one occasion a female was 

 observed to dig a shallow hole about two inches wide and about 

 as deep. Two china-like eggs were laid in the nest and covered up 

 loosely with debris. Sometimes the nest is constructed with some- 

 what greater care, but it is less elaborate than in other species 

 studied. 



Family 4. Platysternidae. This family is represented by one 

 species native to Borneo, Siam, and Southern China. Platysternum 

 is an extremely flat type, with unusually large head and hooked 

 beak. 



Family 5. Testudinidse (the common pond tortoises). This is 

 much the largest family of chelonians and is represented in North 

 America by Graptemys geographica (the map tortoise), Chrysemys 

 picta (the painted tortoise), Nannemys gutatta (the spotted tortoise), 

 Terrapene Carolina (the box tortoise) and, as an aberrant derivative of 

 North American chelonians, the giant land tortoises of the Galapagos 

 and other oceanic islands. In habits they range from aquatic to 

 purety terrestrial forms. Some are purely carnivorous, other purely 

 herbivorous. 



Perhaps the commonest example of our pond tortoises is Chry- 

 semys picta (eastern variety) or C. marginata (western variety). These 

 rather small tortoises are found in ponds or sluggish streams. They 

 are most frequently seen when basking in the sun along the shore or 

 upon floating logs. They are excellent swimmers and somewhat 

 difficult to catch. They feed upon dead fish and other carrion in the 

 water, tearing up the flesh with their long, sharp claws and sharp- 

 edged beaks. The nest is made with a narrow neck and a flask-shaped 

 chamber at the bottom. It is situated in moist sand along the shores 

 of still waters. Four to eight oval eggs are laid; these are placed in 

 the flask-like enlargement and are covered up neatly with sand, which 

 is pounded down with the knuckles of the hind feet. Chrysemys is a 

 bright, intelligent little tortoise, showing little sullenness when cap- 

 tured, and no disposition to snap or to take alarm. They soon learn 

 to come to one who habitually feeds them and will eat from the 

 hand. 



Terrapene Carolina (Fig. 133, F) is the common land terrapin of the 

 Southern and Eastern States. Structurally they differ little from 

 some of the pond tortoises, but they have acquired exclusively terres- 



