23 
having regarded the specimens “as belonging to an extinct species 
of Albatros.” My reference of the bones even to the longipennate 
tribe of natatorial birds is stated hypothetically and with due caution : 
**On the supposition that this fragment of bone is the shaft of the 
humerus, its length and comparative straightness would prove it to 
have belonged to one of the longipennate natatorial birds equalling in 
size the Albatros.” (oc. cit. p. 411.) 
Since the discovery has been made of the manifestly characteristic 
parts of the genus Pterodactylus in the Burham chalk-pit, it has been 
objected that the bones first discovered there, and described by me 
as resembling birds of flight, ‘are so extremely thin, as to render it 
most improbable that they could ever have sustained such an instru- 
ment of flight as the powerful wing of the Albatros, or of any other 
bird: their tenuity is in fact such,” says the ew post facto Objector, 
“as to point out their adaptation to support an expanded membrane, 
but not pinions *.”’ 
The reply to this assertion need only be a simple reference to na- 
ture: sections of the wing-bones of birds may be seen in the Museum 
of the Royal College of Surgeons, and have been exposed to view, 
since the discovery of their structure by the Founder of: that Collec- 
tion, in every Museum of Comparative Anatomy worthy to be so 
called. 
To expose the gratuitous character of the objection above cited, I 
have placed on the table a section of the very bone that directly sus- 
tains the large quill-feathers in the Pelican ; its parietes are only half 
as thin as those of the antibrachial bone of the great Pterodactyle 
which is figured in my ‘ History of British Fossil Reptiles,’ pl. 4, and 
is not thicker than those of the bone figured in the Geological Trans- 
actions, 1840, above cited. 
Hunter, who had obtained some of the long bones with thin 
walls and a wide cavity from the Stonesfield slate, has entered them 
in his MS. Catalogue of Fossils as the “Bones of Birds,” and per- 
haps no practical anatomist had had greater experience in the degree 
of tenuity presented by the compact walls of the large air-cavities of 
the bones in that class. Of all the modifications of the dermal system 
for combining extent of surface with lightness of material, the ex- 
panded feather has been generally deemed the consummation. Well 
might the eloquent Paley exclaim, ‘‘ Every feather is a mechanical 
wonder: their disposition all inclined backwards, the down about the 
stem, the overlapping of their tips, their different configuration in dif- 
ferent parts, not to mention the variety of their colours, constitute a 
vestment for the body so beautiful and so appropriate to the life 
which the animal is to lead, as that, I think, we should have had 
no conception of anything equally perfect, if we had never seen it, or 
can imagine anything more so.” It was reserved for the author of 
the ‘ Wonders of Geology’ to prefer the leathern wing of the Bat and 
Pterodactyle as the lighter form, and to discover that such a structure 
as is displayed in the bone described and figured in the ‘ Geol. Trans.’ 
* Mantell, ‘Wonders of Geology,’ 1848, vol. i. p. 441. 
