the bones either continue throughout life with their component parts unsolidified together, or else indicate by clear marks their lines of union, so that it is always easy to tell the number and configuration of which each is composed.
Thus far the characters which separate a reptile from a bird stand so widely apart—the interval between the highest living crocodile and the nearest living bird (represented by such forms as the New Zealand kiwis, the mooruk of Australia, the cassowary of the Moluccas, and the rheas or ostriches of South America) is of such enormous magnitude—that it would seem needless to entertain any fear of mistaking a member of the former group for one of the latter. Meanwhile let us withhold any decided opinion.
On November 29, 1871, a letter to Prof. Dana, dated from San Francisco, written by Prof. O. C. Marsh, of Yale College, New Haven, Connecticut, announced the discovery of a portion of a large headless skeleton in the upper chalk formation of Western Kansas, consisting of the nearly entire posterior limbs, portions of the haunch-bones, several segments from the neck and tail of the spinal column, and numerous ribs all in excellent preservation. The long leg-bone exhibited on the front aspect of its upper extremity the large crest which, as we have already pointed out, is a remarkably Avian character; along its shaft lay a fibula developed as among the diving birds of the present day, to whose thigh-bone also that of the fossil bore considerable resemblance. The "hock-bone," in presenting a trifid pulley-shaped lower end, was birdlike; while in the oblique arrangement of these divisions it again claimed affinities with the divers, whose toes are articulated in this manner to facilitate the forward stroke of their feet through the water, The external division, however, which projects beyond the other two, and is twice the size of either, is developed in a way unknown in any recent or fossil bird, and the bones of the toe supported by it are peculiarly articulated to produce rigidity and prevent flexion, except in one direction, in order by the interlocking of the bones to increase the strength of the joints during the act of swimming; for the whole limb is unquestionably adapted for rapid motion through water. The haunch-bone presents some resemblance to what is seen among the reptiles, in the permanence as separate bones of some of the portions of which it is composed, and in its not being firmly joined to the spine by bony union as in ordinary birds.
The examination so far of these interesting remains proved that the skeleton was certainly a bird's. On comparing its various bones with the corresponding ones in existing representatives, its affinities, notwithstanding considerable divergences from all known recent or ancient species and genera, were evidently with the swimming-birds, of which it is the largest known exponent, and of these it most resembled the great northern diver, near which, for a time, it received a niche with the appellation of Royal Bird-of-the-Dawn (Hesperornis regalis).
