PROFESSOR HUXLEY'S LECTURES. 



215 



present a great number of exceedingly remarkable peculiarities, to 

 which I may have occasion to advert incidentally as I go on, but 

 which are not met with even approximately in any existing forms of 

 reptiles. On the other hand, reptiles, if they have a covering at all, 

 have a covering of scales or bony plates. They possess no wings ; 

 they are not volatile, and they have no such modification of the limbs 

 as we find in birds. It is impossible to imagine any two groups 

 apparently more definitely and distinctly separated. As we trace the 

 history of birds back in time, we find their remains abundant in the 

 tertiary rocks throughout their whole extent, but, so far as our pres- 

 ent knowledge goes, the birds of the tertiary rocks retain the same 

 essential character as the birds of the present day that is to say, the 

 tertiary bird comes within the definition of our existing birds, and are 

 as much separated from reptiles as our existing birds are. A few 

 years ago no remains of birds had been found below the tertiary 

 rocks, and I am not sure but that some persons were prepared to 



Fig. 2. Hesperobnis Kegalis. (Marsh.) 



demonstrate that they could not have existed at an earlier period. 

 But in the last few years such remains have been discovered in Eng- 

 land, though, unfortunately, in a very imperfect condition. In your 



