212 EXTINGT MONSTERS 
already alluded (see p. 126) to Professor Huxley’s theory that 
birds are descended from Dinosaurs; but though there is much 
to be said in favour of the idea, we prefer, for our part, to wait 
and see what evidence may yet turn up on this subject, and, like 
the Irishman, to “prophesy after the event,’ ¢.e. when further 
discoveries have been made. Sir R. Owen never favoured the 
theory, and, for all palzontologists can tell, it may just as well 
be that both birds and pterodactyls (flying reptiles) are descended 
from a common stock; the one line choosing to fly by means of 
a thin membrane attached chiefly to a single long finger, while 
the others thought they could do quite as well—in fact better— 
by growing feathers on their arms and fingers. ~All great 
problems in Nature are solved slowly, by the patient accumulation 
of evidence; and the one above alluded to is no exception to the 
rule. 
Palzontologists are not without evidence bearing on this 
subject ; so perhaps we cannot do better than state briefly what 
that evidence is, in order to show how near, or how far, we are 
from a final answer to our question. Though no one can yet 
say what the very first bird-type was like, we can, at all events, 
describe the oldest known fossil bird. This is the famous 
Archeopteryx.! 
Time was—and that within the memory of living geologists— - 
when no fossil birds were known in rocks older than the Tertiary 
deposits; but the discovery of Archeeopteryx has changed all that, 
and we now trace back the bird line to the middle of the great 
Secondary or Mesozoic Era. This bird was found in the 
Solenhofen limestone of Bavaria, which is supposed to represent 
the lower part of our English Kimmeridge clay. First, only the 
impression of a single feather was known, to which the late 
1 Greek—Archios, ancient; pterux, wing. 
