ORGANS OF LOCOMOTION. 



85 



across them, so as to snrve the purpose of a wing. In birds 

 the pigeon for exaniple, (Fig. 39,) there are but two fingers 

 which are soldered together, and destitute of nails ; and th*^ 

 thumb is rudimentary. 



176. The arm of the turtle (Fig. 40) is peculiar in havinr , 



■a J: 



Fig. 42. 

 besides the shoulder-blade, two clavicles ; the arm-bone is 

 twisted outwards, as well as the bones of the fore-arm, so 

 that the elbow, instead of being behind, is turned forwa-ds; 

 the fingers are long, and widely separated. In the Sloth, 

 (Fig. 41,) the bones of the arm and fore-arm are very greatly 

 elongated, and at the same time very slender ; the hand is 

 likewise very long, and the fingers are terminated by enor- 

 mous non-retractile nails. The arm of the Mole (Fig. 42) 

 is still more extraordinary. The shoulder-blade, which is 

 usually a broad and flat bone, becomes very narrow ; the 

 arm-bone, on the contrary, is contracted so much as to seem 

 nearly square ; the elbow projects backwards, and the hand 

 is excessively large and stout. 



177. In fishes, the form and arrangement of the bones i.i 

 so peculiar, that it is often difiicult to trace their correspond- 

 ence to all the parts found in other animals ; nevertheless 

 the bones of the fore-arm are readily recognized. In the Cod 

 8 



