548 PALMIPEDES. 
that that bone is the ulna, is nearly the same as in the 
skeleton of the Albatross. 
On comparing the fossil with the lower end of the tibia 
of a large Eagle, we perceive in this bird a prominence 
on each side of the condyle, which does not exist in the 
fossil. In the tibia of the Adjutant Crane, which is 
more nearly of the size of the fossil, and resembles it 
more in the sharper margins of the posterior half of the troch- 
lear boundaries, there is a ridge on each lateral surface. 
In the Albatross there is neither a prominent ridge nor 
process: the sides of the condyle, especially the outer 
one, are as even as in the fossil; but the anterior margins 
of the trochlea are more prominent and thicker in the 
Albatross. 
The only other bone in a bird’s skeleton which has a 
similar trochlear extremity is the metacarpal of the wing, 
the proximal end of which is formed by the confluent os 
magnum. In the degree of obliquity, and the extent of 
the sharp borders of this trochlea, some resemblance to 
the fossil may be traced; but the fossil, in the greater 
antero-posterior extent of the articular surface, with which 
the median groove of the pulley is co-extensive, differs 
much from the metacarpal joint, and agrees with the 
tibial trochlea. Moreover, there is no trace of the process 
which stands out from the radial end of the trochlea in 
the metacarpus, nor of the smaller process for the attach- 
ment of the ligament from its palmar side. 
I am at present unacquainted with any bone of the 
Pterodactyle which presents a deep trochlea, describing 
three-fourths of a circle, as in the fossil; and I therefore 
still regard my original view of the nature of these in- 
teresting fossils, as the most consonant with known ana- 
logies of structure. 
