VERTEBRATA. 



273 



feathers, such as exists in other birds. The extinct 

 reptile called Pterodactyl may also be regarded as a 

 link between the two groups, for it. had . the power of 

 flight. Its wing was not constructed like that of a 

 bird, but appears to have been in some respects like 

 that of a bat, existing as an expansion pQnnected with 

 the digits or fingers, one of which was enormously 



Fig. 102.— Breast-bone and shoulder-girdle of an embryo ostrich of 27 days' 

 incubation, showing reptilian type of coracoid and claws on the wing. (From 

 Ptoc. Zool. Soc, June, 1885.) 



large ; whence the name Pterodactyl, or wing-fingered 

 animal. 



Eeptilian features may bo traced, too, in some birds. 

 The coracoid bone of the ostrich, e.g., consists in the 

 unhatched bird of a wide perforated plate, similar in 

 type to the coracoid of some reptiles, and is but slightly 

 modified in the adult. The ostrich, and one or two 

 other birds also, have claws on the digits of the wing ; 



T 



