Prof. Marsh thinks that probably it possessed bi-concave segments in its backbone, indicating, therefore, some alliance with the ichthyornis. The structure of its wings, Prof. Huxley points out, differs in some very remarkable respects from that which they present in a true bird. In the archæopteryx the upper arm-bone is like that of a bird, and the two bones of the forearm are more or less like those of a bird; but the fingers, which in all modern avian representatives are fused together into one mass, are not bound together—they are free. What the number may have been is uncertain, but several, if not all, of them were terminated by a strong-curved claw; so that in the archæopteryx we have an animal which to a certain extent occupies a midway place between a bird and a reptile. It is a bird in so far as its foot and sundry other parts of its skeleton are concerned; it is essentially and thoroughly a bird by its feathers: but it is much more properly a reptile in the fact that the region which represents the hand has separate bones with claws resembling those which terminate the fore-limb of a reptile. Teeth and a long tail, moreover, have certainly been considered hitherto non-avian characteristics.
More recently in our own country there has been brought to light from the London clay, in the island of Sheppey, a skull with the margins of the jawbones armed with larger alternating with smaller denticulations. It has been submitted to the examination of Prof. Owen, facile princeps among the restorers of osteological remains, who concludes that it belonged "to a warm-blooded feathered biped with wings"—to a bird, in fact—"and further, that it was web-footed and a fish-eater, and that in the catching of its slippery prey it was assisted by the peculiar armature of its jaws." Many living birds, such as the mergansers or saw-bills, have denticulations on the borders of the horny covering of the bill; but no modern bird has ever the underlying bone elevated into ridges or denticulations like those seen in the London-clay fossil. On the palate, however, of the rare Phytotome, a South American perching bird belonging to the group of the Leaf cutters, which bears in its structure many "marks of ancientness," we find two rows of bony denticulations, the remains of what are apparently but recently lost teeth, if we calculate time by the geological horologe, and which may be faint memorials of the dental arrangement seen in the chameleon. Certainly, "they are not the less of interest, seeing that as yet we have nothing else intervening between them and the teeth of the Sheppey fossil." How far this fossil may have resembled any of the avian remains which we have described above, we must wait to know. To conjecture would be dangerous, considering how wide of the mark would have been, in all likelihood, the restoration, had any been attempted, of the hesperornis, whose true structure when revealed so greatly surprised the most experienced naturalists. All that can at present be said is, that the owner of the solitary skull could not have claimed a place within the old avian province. It is