20 Osteological Studies of the Subfamily Ardeincc. 
bular ridge, and merges at last into that part of the shaft which 
is subcylindrical, at juncture of upper and middle thirds. 
At the distal extremity, the shaft enlarges but very slightly, 
and just sufficient to afford a base for the condyles, which here 
project, in consequence, well out in front of it, both before and 
behind, more particularly in the former direction (Fig. 24). 
The “ tendinal bridge ” though present, is not nearly so well 
developed as in some other birds, and in my specimen of Nycti- 
corax a ‘ ‘ bird of the year ” it is not united in the middle, it being 
simply represented by a triangular process on either side, with 
their bases in the margins of the excavation, and their apices op¬ 
posite and nearly touching each other. A tubercle occurs above 
the outer condyle where this bridge abuts on that side, which is 
its lower one, it spanning the tendinal groove rather obliquely. 
The inter-condyloid depression is wide, deepest in front, to 
become narrower and shallower behind, where it ceases as the 
shaft commences. 
Viewed anteriorly, the outer condyle is the broader, extends 
higher on the shaft, but projects no further in front than the inner 
one. This latter, slightly encroaching on the inter-condyloid 
space, is excavated by a well defined subelliptical pit, which is 
better marked in the Night Herons, though present in the Ardeince 
generally. 
Viewed from behind, these condyles of the tibia in Ardea 
mount to points about opposite each other on the shaft. Here, 
however, the inner condyle is the broader, and rather more promi¬ 
nent above. 
Upon lateral aspect these condyles are reniform in outline 
with the convex surfaces below; and from above, downwards, the 
outer is the deeper of the two. 
In in) 7 Osteology of the North American Tetraonidae I 
described the method of ossification of the cnemial crest of the tibia 
in the young of Centrocercus urophasianus. In the memoirs in 
question I gave a figure showing this development, which in brief 
consisted in a large osseous segment engrafted upon the bone, at 
the future site of the cnemial crest and upper halves of the pro- and 
ecto-cnemial ridges, all of which it formed, but left no trace of 
such a develepment in the adult fowl. 
A re-examination of this state of affairs convinces me, that in 
the bird alluded to. the description is correct in every particular. 
