[1] This preoccupation rests, so far as I am aware, upon Marsh’s statement. I can find no evidence of the name having been previously used. =Nyctodactylus gracilis.= _Pteranodon gracilis_ Marsh, Amer. Journ. Sci. xi, p. 508, June 1876. _Nyctosaurus gracilis_ Marsh, Amer. Journ. Sci. xii, p. 480, Dec. 1876. _Nyctodactylus gracilis_ Marsh, Amer. Jour. Sci. xxi, p. 343, April 1881. PTERANODON. =Skull.= Fragmentary portions of the skull of Pteranodon are not at all rare in the Kansas chalk; but it is exceedingly seldom that a complete, or even approximately complete specimen is found. Their great length and slenderness, together with the extensive pneumaticity of the bones, render their preservation, as a whole, a thing of great rarity. Probably the most nearly perfect one yet known is now in the Museum of Kansas University. It was discovered the past summer by Mr. E. C. Case, a member of the University Geological Expedition. The specimen was carefully cleaned on its upper surface, as it lay in the chalk, and then imbedded in plaster before removal. The surface now exposed was the under one, which surface is, almost invariably, better preserved and less distorted than the upper one in these animals. A figure of this specimen is given in Plate I. The only portion restored is that indicated by the line in the lower jaw; it is possible that this part of the symphysis may not be exactly as it is drawn. Other, incomplete, specimens in the Museum confirm the outlines, except in the occipital crest, which is not present. As stated by me in the American Naturalist (_l. c._), the type specimen of _Pteranodon_, also collected by myself, was incomplete, and the figures of it, as given by Marsh, are faulty. The elements of the skull are all so firmly united that they can not be distinguished. There are no indications whatever of a horny sheath enclosing the jaw, and it is improbable that the covering of these parts was essentially different from that in the slender jawed _Pterodactylidae_. In texture, the maxillaries are fine-grained, and wholly without the vascular foramina found in the corresponding bones of birds. The bones are composed of two thin and firm plates, separated by cavities which are bounded by irregular walls of bony tissue. In the compression from which all the Pterodactyl bones have suffered more or less, the greater resistance of these walls has caused irregularities upon both the outer and the inner surfaces. At the borders of the bones, where the thickness has been greater, the roughening is not observed.