BAT. 553 



cordingly we find them consolidated into one (R) ; 

 or rather no part of the ulna is developed, except 

 the process of the olecranon, or elbow, which has 

 become soldered to the radius. 



These advantages in the construction of the 

 fore extremities are obtained at the expense of 

 the hinder, which are too feeble to support the 

 weight of the body in the ugright position 

 required for walking, in consequence of the 

 centre of gravity being between the wings. On 

 a level plane, indeed, the bat can advance 

 only by a kind of crawling or hopping motion. 

 The whole anterior half of the trunk is much 

 more fully developed than the posterior half, 

 which appears as if it had been checked in its 

 growth. The pelvis (p) is of diminutive size, 

 compared with the rest of the skeleton : the 

 pubic bones are lengthened backwards, and are 

 joined merely at a small point. The whole 

 posterior limb is short, the femur (f) compa- 

 ratively long, and the fibula is a very slender 

 bone, yet quite distinct from the tibia (T). 

 The slight degree of motion which is thus al- 

 lowed between them is useful to the animal, 

 in enabling the feet to lay hold of cornices 

 or other projecting parts of the roofs of build- 

 ings, on which the animal fastens itself, and 

 hangs with the head downwards. It is pro- 

 bably with the intention of facilitating this ac- 

 tion that the toes are turned completely back- 



