534 COLLEGE ZOOLOGY 



colored in aquatic turtles. The sense of hearing is fairly well 

 developed, and turtles are easily frightened by noises. The 

 sense of smell enables the turtle to distinguish between various 

 kinds of food both in and out of the water. The skin over many 

 parts of the body is very sensitive to touch. 



2. A Brief Classification of Living Reptilia 1 



The four thousand or more species of living reptiles may be 

 grouped into four orders: (i) the Testudinata, containing 

 about two hundred and twenty- five species of turtles and tor- 

 toises; (2) the Rhynchocephalia, represented by a single New 

 Zealand species; (3) the Crocodilini, containing about twenty- 

 three species of crocodiles, gavials, and alligators; and (4) the 

 Squamata, containing about three thousand seven hundred 

 species of lizards, chameleons, and snakes. In most cases the 

 orders, families, and subfamilies of reptiles are indicated by means 

 of structural characters, such as the position of the teeth, the 

 shape and arrangement of the bones of the skull, and the form 

 of the vertebrae. Since these cannot be determined by the 

 beginning student, they are mostly omitted from the following 

 paragraphs. 



Order 1. Testudinata (Chelonia). — Turtles and Tortoises. 

 — Reptiles with the body incased in a bony capsule; 

 jaws without teeth ; quadrate bone immovable ; usually 

 pentadactyl appendages. 

 Superfamily 1 . Cryptodira. — Testudinata with the 

 carapace covered with horny shields; neck bends in 

 S-shaped curve in a vertical plane; pelvis not fused with 

 the carapace. 

 Family 1 . Chelydrid js. — Snapping-turtles. — Cryp- 

 todira with small plastron; tail long; limbs, neck, 

 and head large and cannot be withdrawn into shell; 



1 1 am indebted to Dr. Alexander G. Ruthven for the main divisions of this 

 classification. 



