williston: kansas pterodactyls. 



Nyctodactylus gracilis. 



Pieranoilon f/rurilis, Mursh, Amcr. Journ. Sci. xi, p. 508, June 187G. 

 NyctosKunis (/ruciUs'K'dx^h, Amer. Joiu-n. Sci. xii, p. 480, Dec. 1876. 

 Nyct<i(hidi/hifi gruciUs 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. Prob- 

 ably 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 spec- 

 imen was carefully cleaned on its upper surface, as it lay in the chalk, 

 and then imbedded in plaster before removal. The surface now ex- 

 posed 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 (/. 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 

 Ptcrodactylid(C. 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 rough- 

 ening is not observed. 



Seen from above, the skull is narrow, as stated by Marsh ; but, con- 

 trary to his statement, there is not a sharp ridge extending along the 

 upper border. This border is obtuse and rounded, and in the frontal 



