PHYLUM CHORDATA 



401 



Class V. REPTILIA (Lat. repcre, to crawl). -- SPHENODON, 

 CHAMELEONS, LIZARDS, SNAKES, CROC A ODILES, 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). -- W T arm-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 

 chordates in their metamerism and bilateral symmetry and in the 



SPINAL CANAL) 



NEURAL TUBE 



SPINAL CORD 



BRAIN 



NOTOCHORD VISCERALTUBE(C0CMV 





mTygvrq 



- /XUIN^ -J^SSS* 1 "" 



tf *Si .^^^^T < 



ab^^efe&3>Xr^M 



> / 



ORAL CAVITY 



J 



STERNAL GILL SLITS 



HEART LIVEK 



AlIiNZ 



NARY DUrr 

 3ENITALDUCT 



SPLEEN 



CLOACA 

 ' URINARY BLADDER 



BILE DUCT 

 PANCREAS 



FIG. 345. Diagrammatic longitudinal section of a vertebrate (female). 



(From Wiedersheim.) 



possession of a ccelom, 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 venlrally situated heart with at 

 least two chambers, and red corpuscles in the blood. 

 2 D 



