STUDIES OE THE MACROCHIRES. 337 
both, on the other hand, are extremely unlike- the pectoral girdle 
as we find it in Geococcyx. 
These remarks apply with equal truth and force to the 'pectoral 
and pelvic limbs of the several forms under examination ; and 
even in the case of the reversion of the toes in Trogon and the 
Ground-Cuckoo, we are all aware that in the former bird the 
second toe is turned back, while in the latter it is the fourth 
one that is reversed. 
I agree entirely with Professor W. K. Parker when he 
states that “ the familiar term ‘ zygodactyle ’ for birds with a 
certain form of foot has been very useful; and yet huw much 
ignorance it may be made to hide ! It seems to be something 
when one knows that a certain bird belongs to that group ; and 
yet a Cuckoo, a Parrot, and a Woodpecker come none the nearer 
each other zoologically by the possession of that kind of foot 
To recapitulate then, and judging from the skeletons alone , we 
must see that such a form as Geococcyx californianus is more or 
less remotely related to such birds as Alcedo and Dacelo , 
perhaps much nearer them than it is to the true Tree-Cuckoos. 
In saying this I am aware that in a paper recently read for me 
before, the Zoological Society I was still inclined to support 
the classification of Garrod, who divided the Cuculidce into two 
subfamilies, viz. the Ground-Cuckoos ( Centropodince ) and the 
true Cuckoos ( Cioculince ) (P. Z. S. 1874, p. 121) ; and this paper 
of mine referred to the anatomy of G. californianus , but at the 
time I had no specimens of true Cuckoos to compare it with. 
Still I am inclined to adhere to that opinion until I have had an 
opportunity of making further researches into the structure of 
many other types more or less nearly related. » On the face of it 
I should be disposed to think that Geococcyx , so far as its skele- 
ton is concerned, came nearer to such a form as Dacelo yiyantea 
than to Cuculus canorus, for instance, notwithstanding the 
structure of the foot. But many of these interrelated groups 
are exceedingly puzzling, and still require a considerable amount 
of original investigation of their morphology. 
Of the Caprimulgi, of course, I shall have more to say further 
on ; it is very evident, so far as their osteology indicates, that 
they are very widely separated from the Trogons. 
And now as to the Trogons themselves, still being guided by 
* Parker, W. K., “ On the Morphology of the Skull in the Woodpeckers 
and Wrynecks,” Trans. Linn. Soc., Zool. 2nd ser. vol. i. pp. 1-22. 
