6 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
marked humeral crest, evidently possessed great powers 
of flight, equal at least to the great majority of birds at 
the present day. So that, even in the Cretaceous period, 
fully developed flying and flightless birds existed side by 
side, and the problem is simply thrown further back. The 
earliest known fossil bird, I may say, the Archeopteryz, 
from the Triassic deposits of Bavaria, although presenting 
many reptilian features, was nevertheless a true bird, 
possessing well-formed feathers; so that birds have clearly 
a greater antiquity than used to be thought, and we must 
go back to Triassic, and probably even to Paleozoic, times 
in order to get at the original avian ancestor from which 
all other birds have been derived. 
Before leaving Hesperornis, it is very interesting to 
observe the small size of the brain of this bird. Com- 
paring it, as Marsh has done, with the brain of a modern 
Diver, the superiority in size and complexity of the latter 
is very marked. Precisely similar results were obtained, 
by the same investigator, in comparing the brain cavity of 
Ichthyorms with that of a modern Tern, to which bird 
Ichthyornis is considered to be most nearly allied. 
I think that hardly sufficient importance has been 
attached to this highly pregnant fact, namely, the steadily 
increasing size and complexity of the brain in birds, as we 
pass from Mesozoic to modern times, without, so far as 
we can judge, a corresponding increase in the complexity 
of other parts of the body; for, to my mind, the gradual 
increase of brain power which has been going on for past 
ages accounts for not a little of the silent extinction of 
species which is written large on every page of the 
geological record. 
With this digression, I pass to the second section of my 
first group of flightless birds, which comprises birds in 
which the lower extremities have been specially developed 
