The most interesting of all the English Pterodactyle remains is the small fragment of jaw figured by Sir Richard Owen in 1859, which is a little more than two inches long and an inch wide, distinguished by a concave palate with smooth rounded margins to the jaws and a rounded ridge to the beak. It is the only satisfactory fragment of the animal which has been figured, and indicates a genus of toothless Pterodactyles, for which the name Ornithostoma was first used in 1871. After some years Professor Marsh found toothless Pterodactyles in Kansas, and indicated several species. There are remains to the number of six hundred specimens of these American animals in the Yale Museum alone; but very little was known of them till Professor Williston, of Lawrence, in Kansas, described the specimens from the Kansas University Museum, when it became evident that the bones of the skeleton are mostly formed on the same plan as those of the Cambridge Greensand genus, Ornithocheirus. They are not quite identical. Professor Williston adopts for them the name Ornithostoma, in preference to Pteranodon which Marsh had suggested. Both animals have the dagger-shaped form of jaw, with corresponding height and breadth of the palate. The same flattened sides to the snout, converging upwards to a rounded ridge, the same compressed rounded margin to the jaw, which represents the border in which teeth are usually implanted, and in both the palate has the same smooth character forming a single wide concave channel. Years previously I had the pleasure of showing to Professor Marsh the remarkable characters of the jaw, shoulder-girdle bones, and scapulæ in the Greensand Pterodactyles while the American fossils were still undiscovered. I subsequently made the restoration of the shoulder-girdle (p. 115). Professor Williston states to me that the shoulder-girdle bones in American examples of Ornithostoma have a close resemblance to those of Ornithocheirus figured in 1891, as is evident from remains now shown in the British Museum. It appears that the Kansas bones are almost invariably crushed flat, so that their articular ends are distorted. The neck vertebræ are relatively stout as in Ornithocheirus. The hip-girdle of the American Ornithostoma can be closely paralleled in some English specimens of Ornithocheirus, though each prepubic bone is triangular in the American fossils as in _P. rhamphastinus_. They are united into a transverse bar as in Rhamphorhynchus, unknown in the English fossils. The femur has the same shape as in Ornithocheirus; and the long tibia terminates in a pulley. There is no fibula. The sternum in both has a manubrium, or thick keel mass, prolonged in front of its articular facets for the coracoid bones, which are well separated from each other. Four ribs articulate with its straight sides. The animal has four toes and the fifth is rudimentary; there are no claws to the first and second.