AND PHYSIOLOGY. 99 



valuable instruments of progression, since in many they can 

 be placed upon the ground and used as feet. 



214. Shell of Tortoise, — In the Tortoise that portion 

 which is commonly called the shell, is made up of the Cta*ft 



Fig. 110. 



p f 



Skeleton of the Tortoise ; the Plastron has been removed, vc. Cervical Vertebra 

 vd. Dorsal Vertebra, c. Ribs. cs. Sternal Ribs. — The Marginal Bones of the C»ra. 

 pace: o. Scapula, cl. Collar Bone. co. Coracoid Bone. b. Pelvis. /. The Femur. 

 t. Tibia, p. Fibula. 



pace or upper portion, and the Plastron, or lower one. The 

 Carapace seems to be a mere expansion of the vertebrae, and 

 the Plastron an expanded sternum. Hence, as the annexed 



214. What is the Carapace and what is the Plastron in the Turtlo family ? From what 

 bones are they developed ? 



