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TEXTBOOK OF ZOOLOGY 



space is relatively great in some turtles. This enables them to remain 

 submerged for considerable periods. Accessory urinary bladders also 

 serve in aquatic respiration. 



Marq'inals 

 Scapula 



Humerus 



Radius — 



Entoplasbron 



Epiplastron 



Tibia ---rJi 

 Fibula - ■ 



)(\pHp\aslrov\ 



Suprapygal 



Fig. 304. — Skeleton of the turtle, Pseudemys troostii elegans, showing ventral view 

 of carapace and dorsal view of plastron. 



Circulatory System 



The circulatory system of the turtle consists of the heart, arteries, 

 connecting capillaries, and veins. 



The heart is typically reptilian in structure, having two auricles 

 and one ventricle with a perforated partition dividing it. The pul- 

 monary circulation returns blood to the left auricle, but this aerated 



