i CHELONIAN REPTILES. 327 



humerus is remarkably curved, especially in the tortoise, 

 where it has the form nearly of a semi-circle. The radius 

 and ulna are distinct from each other; the carpus and pha- 

 langes are short and stunted, forming a compressed kind of 

 hand. 



The pelvis, like the scapula and clavicle, is enclosed with- 

 in the bony shell which protects the trunk. The sacrum is 

 moveable upon the last dorsal vertebra; and the coccygeal 

 vertebrae are continued from it, forming a short tail. The 

 femur is short and powerful, and somewhat bent, but less so 

 than the humerus; and the rest of the bones of the hind ex- 

 tremity are similar to those of the fore leg.* All the feet 

 are joined obliquely to the limbs which support them, giving 

 the animal an apparent awkwardness of gait, as if it were 

 obliged to walk upon club feet. The impulse which they 

 give being lateral and oblique, renders them more efficacious 

 for progression in the water than on land: this circumstance, 

 in conjunction with the constitutional torpor of the animal, 

 sufficiently accounts for the excessive, and, indeed, proverbial 

 tardiness of its movements. 



Security appears still to be the object aimed at in the me- 

 chanism of all the other parts of the skeleton. The articu- 

 lations at the shoulders and the hips are such as facilitate 

 the complete retraction of the limbs within the carapace. 

 After the head has been drawn in by the double, or serpen- 

 tine flexion of the neck, the knees are brought together, and 

 the whole limb withdrawn within the shell, the fore legs 

 folding completely over the head, so as to cover and protect 

 it most effectually. For this purpose, the carpus and meta- 

 carpus are exceedingly flattened, and approximate to the lin- 



in the skeleton, the several pieces whicli correspond to the normal type of 

 the scapula, acromion, coracoid bone, and clavicle; and anatomists arc not 

 yet ag-recd as to the proper designations which are applicable to these bones, 

 in the Chelonia. 



* The cylindrical bones of the tortoise are solid throug-hout, and have no 

 cavity for containing- marrow, as in the more hig-hly developed bones of the 

 mammalia. This is seen iu the section of the femur, Fig'. 214. 



