Order 8 Odonata ("toothed"). Four elongate, net-veined wings, 

 almost exactly alike; incomplete metamorphosis; large biting mouth. 

 Examples, dragon flics, damsel flies. 



Order 9 Isoptera ("equal-winged"). Four leathery wings of equal 

 width; incomplete metamorphosis; biting mouth; whitish lx)dy. 

 Example, termites (see illustration, p. 179). 



Order 10 Neuroptera ("net wings"). F'our elongate wings with 

 cross-veins; complete metamorphosis; biting mouth. Examples, ant- 

 lions, aphis-lions. 



Order 11 Suctoria ("sucking"). No wings; complete metamor- 

 phosis; sucking mouth; body flattened from side to side; hind legs 

 fltted for jumping. Example, fleas. 



Order 12 Siphunculata ("tube"). No wings; incomplete meta- 

 morphosis; sucking mouth; body flattened from top to bottom. 

 Examples, lice, cooties. 



PHYLUM X MOLLUSKS ("soft"). Unsegmented, soft-bodied animals, most 

 of them bearing shells. The most important classes are 



CLASS 1 GASTROPODS ("belly-footed"). Having shells of a single piece. 



CLASS 2 PELECYPODS ("hatchet-footed"). Bivalve, that is, shells have 

 two valves. Examples, oysters, piddocks, scallops, mussels, shipworms, clams 

 (see illustrations, pp. 32 and 209). 



CLASS 3 CEPHALOPODS ("head-footed"). The foot partly surrounds 

 the head and has a number of arms, or tentacles. Examples, octopus, cuttle- 

 fish, squid, nautilus. 



PHYLUM XI CHORDATES ("cord"). Animals having an internal axial basis 

 for a skeleton, called a notochord, from which the vertebral column develops. A 

 number of small animals have this structure, which suggests the beginning of 

 such a column, but never develop a true backbone. Examples, acorn worm, 

 lancelet, sea squirt. These animals are included among the chordates in subphyla 

 distinct from the vertebrates. All the common large animals are vertebrates. 



SUBPHYLUM VERTEBRATES ("joint" or "turning"). Includes all animals 

 with segmented backbone. The five important classes are as follows: 



CLASS 1 PISCES ("fish"). Fishes are aquatic, cold-blooded animals; they 

 have a two-chambered heart. The stone hag and the lamprey are sometimes 

 called fishes, though they are distinct in having sucking mouths, no jaws, no 

 side fins, and a smooth skin without scales. They never develop bones; the 

 skeleton is of cartilage. 



Order 1 Elasmobranchs Cartilage skeleton; platelike gills; no gill 

 covers; no air bladder. Examples, skates, rays, sharks. 



Order 2 Ganoids Armored fishes; large bony scales in skin, es- 

 pecially around the head; have gill covers and air bladders. Examples, 

 sturgeon and gar pike (see illustration, p. 457). 



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