PHYLUM CHORDATA 



401 



Class V. Reptilia (Lat. re per e, to crawl). — Sphenodon, 

 Chameleons, Lizards, Snakes, Crocodiles, and Turtles 

 (Figs. 439-469). — Cold-blooded vertebrates breathing by means 

 of lungs and usually having a scaly skin. 



Class VI. Aves (Lat. avis, bird). — Birds (Figs. 470-509). — 

 Warm-blooded vertebrates with the fore limbs modified into 

 wings and the body covered with feathers. 



Class VII. Mammalia (Lat. mamma, breast). — Hairy Quad- 

 rupeds, Whales, Seals, Bats, Monkeys, and Man (Figs. 510- 

 550). — Warm-blooded vertebrates with a hairy covering at 

 some stage in their existence; the young nourished after birth 

 by the secretion of the mammary glands of the mother. 



Plan of Structure. — The vertebrates resemble the other 

 chorda tes in their metamerism and bilateral symmetry and in the 



NEURAL TUBE (CtREB/10 SPINAL canal) 



SPINAL CORD N0T0CH0RD VISCERAL 1\)BI(C0U0M£J 



U CAVITY/ 



f TERNAl GILL SLITS, 



HEART 



OACA 

 URINARY BLADDER 



•Bile: duct 

 pancreas 



Fig. 345. — Diagrammatic longitudinal section of a vertebrate (female). 



(From Wiedersheim.) 



possession of a ccdom, a notochord, and gill-slits at some stage 

 in their existence, and a dorsal nerve tube. , They differ from other 

 chordates and resemble one another in the possession of carti- 

 laginous or bony vertebra, usually two pairs of jointed appendages 

 containing a central skeleton, a ventrally situated heart with at 

 least two chambers, and red corpuscles in the blood. 



2 D 



