FLIGHTLESS BIRDS. 5 
fore-arm are presumed to have been non-existent, as no 
trace of them has been found, and the humerus, at its 
distal extremity, presents no trace of articular facets. It 
is possible, however, that they may have existed, although 
in a very rudimentary form. As before mentioned, Hes- 
perormis is now usually classed with the Divers, but it 
is quite possible that the characters, such as the long, 
narrow pelvis, &c., upon which reliance is placed, may be 
purely adaptive in nature, and acquired owing to similar 
habits of life. It is not by any means always easy to 
distinguish between characters which are simply adaptive 
and those which indicate community of origin; and a 
small character, such as the single upper articular head of 
the quadrate bone, which is characteristic of almost all 
the Ratite, may really be of more importance as indicating 
blood relationship, than the more striking features of the 
pelvis, &c. 
Lately, indeed, a remarkably perfect specimen of Hes- 
perornis has been disvovered, with the feathers in place, 
and these are stated by Marsh to resemble the typical 
plumage of the Ostrich. So that, possibly, the earlier 
view, that of the discoverer, may yet prove to be the more 
correct, and Hesperornis may find its nearest allies in the 
Ratite. 
The fact that this bird presents us with an example of 
a smooth sternum and functionless wing, occurring as far 
back as Mesozoic times, has been held by some to support 
the view that the Carinate birds passed through a Struth- 
ious stage prior to attaining their present development. 
Unfortunately for this view, however, in so far as it rests 
upon Hesperornis, there are found side by side with this 
bird, in the same Cretaceous beds, fossil remains of a bird, 
Ichthyornis, resembling a Tern, which, from the great 
development of the keel of the sternum and the strongly- 
