On the Osteology of Nyctosaurus. 143 



deeply concave surface on the inner side. Just in front of this, near the 

 middle of the bone, transversely, there is a pneumatic foramen on the 

 flexor side. The inner side of the bone, at this extremity is expanded 

 into a thin, convex process. The articulation at.the distal extremity can- 

 not be made out, as it is largely concealed by the carpals. The shaft is 

 nearly straight, curved forward gently at the distal extremity. 



measurements. 



mm. 



Length 144 



Width of proximal extremity - — 44 



Width of shaft -• •- 24 



Radius. PI. XLI, Fig. 2, PI. I. The radius is a more slender and 

 slightly shorter bone than the ulna. On the left side it lies partly con- 

 cealed beneath the ulna and there would seem to have been no pronation 

 of the bone. The bone is more slender than the radius, somewhat concave 

 along its inner or upper border as it lies in relation with the ulna; nearly 

 straight as it lies compressed from above downward. The bone is more 

 expanded distally than proximally. The proximal articular surface is 

 rounded and concave. Lying near the roughened distal surface shown 

 in the figure there was a small sesamoid bone. 



MEASUREMENTS OF RADIUS. 



mm. 



Length - 140 



Width of shaft middle third . 18 



Width distal extremity 24 



Carpals. PI. XLII, Figs. 2, ed t 3, PI. XLIV, Fig. 8. The two chief 

 carpals of the left wrist are in relation with each other and the wing meta- 

 carpal, and but slightly displaced from the forearm bones. On the right 

 side they are separated, and the proximal one is partly concealed beneath 

 the ischium, the distal one having its proximal surface obliquely exposed. 

 In the figure (PI. XLIV, Fig. 10), the one shown obliquely is that of the 

 other carpus figured. The wing metacarpal of the left side (PI. XLIV, Fig. 

 2), lying articulated with the distal carpal, has the under side uppermost, 

 from which it would appear that the view given is of the anterior side of 

 the carpus. The proximal carpal is much the larger, extending on the 

 under side either to articulate with the metacarpal, or nearly so. A sub- 

 angular space is left between the two bones on the radial side, for the 

 articulation of the lateral carpal or metacarpal of the first digit. This 

 latter bone, of the right side, is shown in PI. XLII, Fig. 3. It is a small, 

 elongate bone, with an articular emargination on one side, which I had 

 supposed was for the pteroid. I give, also, a good figure of this bone 

 of Pteranodon, copied from Cope (Cretaceous Vertebrata, Plate VII, 



