24 ELEMENTARY ZOOLOGY. 



Aquatic; segmented Annulata (Small). 



Aquatic; not segmented Flat worms. 



With paired appendages, (usually) well-developed. 

 More than two pairs. 



Chiefly air-breathing, though some live in water. 

 Three pairs of legs on thorax (with or without 



wings) Arthropods (Insects). (See p. 265.) 



Four pairs of legs (no wings) Arthropods (Spiders). 

 Several pairs of 1 Annulata (Po i ych(Bta; p . 204 ). 

 legs;segments Arthropods (Myriapoda;?. 265). 

 of the body \ Arthropods (larval insects, as 



lake m grUbS> cater P illars > etc ' ) - 



Chiefly water-living (occasionally air-breathing), 



Arthropods (Crustacea) . 



Large (with heavy shell) Crayfish, crab, etc. 



Smaller, and very varied in form . . Water-fleas, etc. 

 Two pairs of appendages (or fewer) . . Vertebrates (p. 279). 



Appendages fin-like Fishes (p. 294). 



Appendages not fin-like. 



Body smooth and slippery; no scales. .Amphibians. 

 With tail; one or both pairs j Tad 1<JS (larve) 

 of appendages may be SalamanderSm 



lacking J 



Without tail; 2 pairs of legs Toads and frogs- 



(adult) 

 Body covered with scales, or with bony plates, 



Reptiles. 



Scales, and no legs Snakes. 



Scales, and two pairs of legs Lizards. 



Plates fused into a box ; 2 pairs of legs . Turtles, etc. 

 Body producing hair, wool, or fur . Mammals (p. 356.). 

 Body covered with feathers Birds (p. 340.). 



35. Practical Exercise. Select ten kinds of animals known to you, 

 and trace them out to their phyla, and to their classes wherever 

 possible, by means of the above key. 



Recall carefully just what steps you took in doing this work and 

 indicate what powers and processes of your own mind get exercise 

 in it. 



Take ten unknown animals, furnished by the teacher, and trace 

 them to their phyla. 



