STUDIES OE THE MACROCHIRES. 
333 
articulation with the shaft of the tarso-metatarsus at its most 
usual site. 
Measuring the lengths of the several bones of this pelvic limb, 
as we did in the case of the pectoral one, we find that the femur 
is 2'3, the fibula 2T, the tibia 3'3, and the tarso-metatarsus 1'6 
centimetres long. 
Without measuring the several lengths of the joints of the 
pedal digits of a Trogon, I am enabled to say that they are quite 
as harmoniously proportioned as are the corresponding phalanges 
of the average foot of any Passerine bird that I have ever 
examined. 
This completes my description of the skeleton of T. mexicanns , 
and, as observed, it will apply with almost equal exactness to the 
skeleton of T. yuella. In proceeding with my account I have 
been careful, I believe, in every instance to point out any con- 
stant character that seems to distinguish them ; and no doubt 
my description will practically answer for other nearly related 
species of this handsome group of birds. 
It seems scarcely necessary to tabulate the salient features of 
the osteology of this Trogon here, as my brief account presents 
but little more than an enumeration of the essential charac- 
teristics. It will therefore be omitted, in the belief that the 
several figures illustrating my text and the description will be 
amply sufficient even for convenience of reference. 
Comparing these osteological characters of Trogon with the 
corresponding ones of such a Humming-bird as T. Alexandria as I 
presented the latter in my former memoir, P. Z. S. 1885, it will 
at once become evident to us that, so far as the skeletology of 
the two forms is concerned, there is absolutely little or nothing 
that mutually characterizes them. 
So much for the comparative osteology of Humming-birds and 
Trogons, but this will not exactly apply to some other groups of 
birds, such, for example, as the Cuckoos and Nightjars ; and I 
will now proceed to draw a few comparisons among some of 
them. 
I regret to say that the only Cuckoo-like bird I have at hand 
is Geococcyx calif or nianus, and, as stated above, I have already 
published an account of its osteology in the £ Journal of Ana- 
tomy.’ I did have, not long ago, a fairly good skeleton of 
the Yello w-billed Cuckoo ( Goccyzus americanus ) ; but Prof. 
Parker was at that time in search of all the Cuculine birds 
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