REPTILIA 237 



jaws upon it, the victim is doomed, for once closed the jaws are like 

 a steel trap. 



While the ordinary snapper may reach a weight of twenty pounds 

 the alligator snapper grows to twice that weight or more and is 

 proportionately more ferocious. It is said that a large specimen is 

 capable of biting off a piece of board over an inch in thickness. 



Family 2. Dermatemydae. This is a small group of mostly 

 Central American tortoises, with a strictly aquatic habitat. They are 

 primitive in having a row of scutes between the marginals and plas- 

 trals, called inframarginals. This row is represented by the merest 

 vestiges in other families of Chelonia. 



Family 3. Cinosternidae (Skunk or Musk Turtles). This is 

 another group that is primarily aquatic, but not so exclusively so as 

 the first two families described. They are small turtles (Fig. 133, D) 

 that show in their structures evidence of having reverted to an aquatic 

 abode after a prolonged ancestry upon the land. Their box-like shell 

 is not the type of armature that is characteristic of the really aquatic 

 turtles. The commonest representative of the group is Aromochelys 

 odorata, a name redolent of the peculiar sickening odor that it gives 

 off from the inguinal glands when disturbed. The " stink pot," as it 

 is commonly called, lives at the bottom of ponds, crawling over the 

 mud, but seldom swimming freely in the water. Its heavy shell makes 

 it a sort of chelonian diver. In warm weather it is often seen floating 

 at the surface supported upon a mass of floating pond-scum. They 

 rarely bask openly above the water. On land they are slow and clumsy 

 of gait, but in spite of this they wander about at night through the 

 grass and shore herbage, hunting for worms and slugs. I have also 

 found them in the daytime rooting about in the moss for insects or 

 grubs, using their snouts for the purpose and snuffing like little pigs. 

 Sometimes they stay out of water so long that they become light in 

 weight from desiccation. When caught they make a great show of 

 fierceness, hissing and opening the jaws widely, looking almost as 

 formidable as a small snapper; but this is either a mere "bluff" or 

 due to fright, for when given the opportunity to bite they do not take 

 advantage of it. Their appetite is insatiable and indiscriminate; 

 anything that could by any stretch of courtesy be described as edible 

 meets with their approval. Aromochelys is a curious mixture of a 

 primitive and specialized turtle. It is very aquatic at certain times 

 and decidedly terrestrial at others. It pretends to be fierce, but i& 



