Page:Popular Science Monthly Volume 10.djvu/227

 Rh 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 present 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



demonstrate that they could not have existed at an earlier period. But in the last few years such remains have been discovered in England, though, unfortunately, in a very imperfect condition. In your