204 



PICTURESQUE SKETCHES 



to give additional strength to the head, a set of bony 

 tendons running along the vertebrae for this purpose. 

 The length of the neck corresponds with what we see 

 in birds, and indicates a perfect adaptation of the 

 animal for rapid and long-continued flight. In one 

 specimen the head is thrown back so far, that the 

 base of the skull almost touches the tail, without the 

 bones appearing to be in an unnatural position. 



The number of vertebral bones in the back is very 

 considerable, and nearly three times that of birds. 

 In this respect, and in the thread-like form of the 

 ribs, so unlike the broad and flat plates of bone ex- 

 hibited in birds, the analogies are with the lizard 

 tribe; but, on the other hand, the tail possesses only 

 twelve or thirteen vertebrae, and so far is bird-like. 



But it is chiefly in the bones of the extremity, by 

 means of which the animal was enabled to fly, at 

 the same time retaining the power of walking and 

 in all probability of swimming, that we find the 

 most singular of the mechanical contrivances, and 

 observe a structure different from that of any other 

 species, either living or extinct. 



The bones which support the wings of a bird ex- 

 hibit, in spite of great external difference, a good deal 

 of similarity to the bones of the fore extremities of 

 quadrupeds, and even reptiles; and it might have been 

 expected, that, in adapting a species of either of these 

 latter classes for flight, and enabling it to live chiefly 

 in the air, similar modifications would have been ad- 

 hered to. But the fact is not so. The wings of a 

 bird owe a great part of their efficacy to the feathers 

 with which they are covered ; and, as it did not enter 

 into the plan of nature to provide quadrupeds or rep- 



