260 



HOW DO WE CLASSIFY ANIMALS? 



Cthelonioc 



turtle 



Lacertilicc 



1 X ^ ex ]p*ot^ 



Order 1. Chela' ' nia (turtles and tortoises). Flattened reptiles with body inclosed in bony 

 case. No teeth or sternum (breastbone). Examples: snapping turtle, box tortoise. 



Order 2. Lacertil'ia (lizards). Body covered with scales, usually having two-paired ap- 

 pendages. Examples : fence lizard, horned toad. 



Order 3. Ophid'ia (snakes). Body elongated, covered with scales. No limbs present. 

 Examples : garter snake, rattlesnake. 



Order 4. Crocodil'ia. Fresh-water reptiles with elongated body and bony scales on skin. 

 Two-paired limbs. Examples : alligator, crocodile. 



Self-Testing Exercise 



Reptiles are animals which have (1) or (2) plates 



developed from the (3). They always breathe by means of ! 



(4) (5), (6), (7), (8), 



and (9) are examples of reptiles. 



PROBLEM VIII. WHAT ARE THE CHARACTERISTICS OF 



BIRDS? 



Adaptations of birds. Birds are distinguished from all other 

 animals by their covering of feathers and by the modification of 

 the fore limb into a wing for flight. Hollow bones, feathers, and 

 air sacs inside of the body cavity give buoyancy to the body and 

 aid it in staying up in the air. The body is conically-shaped. 

 The tail acts as a rudder. The bill is horny and adapted for 

 securing food. The legs show variations for running, perching, 

 scratching, or swimming. 



The wing is a modified arm, with the fingers very much reduced. 

 To the posterior edge of the wing are fastened long quill feathers 

 which overlap and make a broad, stiff surface for pressing against 

 the air. The wing is jointed and moves in flight like a horizontal 

 figure eight. Powerful breast muscles are attached to the wing 



