On September 26, 1872, Silliman's American Journal of Science announced the disinterment of another skeleton from the chalk of Kansas, "one of the most interesting of recent discoveries in paleontology." The remains included, among other bones, a number of biconcave vertebræ, that is, having the bodies, or solid central piece of the spinal segments, cup-shaped at both ends, a configuration which obtains, as every one has observed, in the divisions of the backbone of the common cod. This characteristic of the spine is frequent enough among reptiles; but it never occurs among birds met with nowadays. If among them there be any tendency that way, as there is in a few birds, the concavity is invariably found in the posterior end, the rarest form of vertebræ among reptiles. "The neck, back, and tail vertebræ preserved, all show this character, the ends of their bodies (centra) resembling those in the plesiosaurs;" notwithstanding the strongly non-Avian description of the spine, all the other bones—the prominently keeled breastbone, the collar-bone united to form a "merry-thought," as well as the leg-and long wing-bones—exhibit those marks which we have found to be most typical of the bird tribe. The wings were large in proportion to the posterior extremities; and the lower end of the leg-bones is incurved as in swimming-birds. Prof. Marsh, therefore, judging from their relative proportion, concludes that the bones belonged to a bird about the size of a pigeon, in many respects resembling the aquatic birds. He has christened it Ichthyornis dispar.
In October of the same year this indefatigable geologist once more announced through the pages of Silliman a new "find" from his favorite and fruitful mine in Upper Kansas. This time it was "a new reptile from the cretaceous. . . a very small saurian, which differs widely from any hitherto discovered." The only remains found on this occasion were two lower jaws, nearly perfect, and with many of the teeth in good preservation. The jaws resemble in general form those of an extinct family of marine reptiles whose remains were first found in the chalk formation near Maestricht; but apart from their very diminutive size they present several features which no species of that group has been observed to possess. Noticeably, the teeth are implanted in distinct sockets, and are directed obliquely backward. There are apparently twenty in each jaw, all compressed, with very acute summits. Then there is no distinct groove on the inner surface of the jaws as in all known Mososauroids—as the family of Maestricht reptiles is named. "Clearly," says Prof. Marsh, "the specimen indicates a new genus."
A more careful removal of the surrounding shale brought to light a fact that enormously enhanced the importance and value of this "most interesting of recent discoveries in paleontology." The jaws, which had been accredited to "a new genus" of reptiles, belonged most undoubtedly, from the position in which they were found with reference to the other bones, to the Ichthyornis dispar, which owned the spine