TURTLES AND TORTOISES 31 



is about five inclies. In Iiabits tliis species seems to be 

 more j^ersistentlj^ aquatic tlian the American turtle. 



Another step up the scale of evolution! We are con- 

 fronted by strictly terrestrial chelonians, but are still 

 considering the turtles. The genus Cistudo is com- 

 posed of six American turtles that have forever left the 

 water ; they lead the same life as the true tortoises. We 

 cannot call them tortoises as they yet have well-defined 

 traces of webs on the hind feet. Their race will ulti- 

 matelj' develop into tortoises; at this stage of their de- 

 velopment we must at once note the high, globular shell, 

 the thick and stubby front feet, and the slow gait, like 

 that of the species of Testudo. 



The Box Turtles are rightly named. Attached to 

 the carapace by elastic cartilage, the plastron is divided 

 by a cartilaginous hinge. We find practically the same 

 structure as observed with EmySj but so perfectly devel- 

 oped that the animal is encased in a veritable, tightly- 

 closed box in time of danger. In most cases the plastral 

 lobes close so tightly against the lower margin of the 

 carapace that it is impossible to insert a broom-straw 

 at anj' part of the union. JNIoreover, the strength of the 

 muscles that draw up the di^'isions of the plastron is 

 astonishing. Ingenuous, indeed, has been Nature in 

 protecting these creatures. 



Five of the Box Turtles inhabit the central and eastern 

 portions of North America ; one occurs in ^Mexico. The 

 maximum length of shell is about seven inches. 



The Common Box Turtle, Cistudo Carolina, has a 

 moderately oval shell with a distinct though flattened 

 keel. There are four claws on the hind foot. While 

 the markings are extremely variable, they are alwavs 

 thick and blotchy, often forming broad yellow E's on 

 the side of the shell. Most of the males have bright red 



