100 FOSSIL REPTILIA OF THE 



similar to what may be seen on the smooth inner surface of an air-bone in a large 

 flying-bird, the Pelican or Adjutant Crane, for example : but it is not peculiar to 

 bird's bones. I find, for example, something of the same character on the smooth 

 inner surface of the medullary cavity of the tibia of a young gavial ; and on the 

 same inner surface in a femur of a lion ; only here there are minute vascular per- 

 forations leading to the thick parietes of the bone, which do not exist in the bird's 

 bone, or in the fossil in question. The enlarged end of the portion of bone, T. XXIV, 

 fig. 3, shows evidence of a light open cancellous structure. 



The thickness of the compact wall of the large medullary cavity does not exceed 

 half a line, as is shown in fig. 3 ; it is a little thicker towards the smaller end of 

 the large bone, figure 1 . In neither case does it exceed the thickness of the shaft of 

 the humerus or ulna of the Pelican. 



The transverse section of the smaller end of the portion of the largest bone, 

 T. XXIV, fig. 1, is a moderately long ellipse, rather more pointed at one end than 

 at the other, indicating an approach to something like a ridge or angle along the 

 corresponding side of the bone. The transverse section of the slender part of the 

 smaller fragments also gives a long ellipse. Neither of the bones show the three- 

 sided figure which characterises the long bone ascribed to the Pterodactylus Cuvieri, 

 T. XXX, figs. 1 — 3, or that, fig. 4 of the same plate, originally figured in the 

 'Geological Transactions,' 2d series, vol. vi, PI. 39, fig. 1. 



The bone with which the larger portion, fig. 1, T. XXIV, is best comparable, is 

 the humerus, of which it may be the distal portion ; but much is wanted in order 

 to attain to a satisfactory determination of it. 



On the supposition that it is part of the humerus, and that the other two portions 

 on the same block of chalk are parts of one bone, this bone may be the shaft of the 

 radius. 



T. XXX, fig. 5, represents, of the natural size, in the same block of chalk, portions 

 of two longitudinally juxtaposed bones, of nearly equal size, and of similar form, and 

 in this respect, resembling the radius and ulna of the Pterodactyle, as they are shown 

 in the Pt. longirostris of Collini and Cuvier,* the Pt. medius of Count Munster,f and the 

 Pt. crassirostris of Goldfuss. j Of one of these bones an extent of upwards of nine inches 

 is preserved in three successive portions. About four inches of the other bone is 

 preserved. Both this and the chief part of the adjoining bone gradually expand to 

 the natural articular end, of which, however, only a small part is preserved in each, 

 showing a shallow smooth concavity; this which is best preserved in the bone, fig. 5*, d, 

 obliquely overlaps a small part of the longer bone. The long diameter of the 

 extremity of the shorter portion of bone is one inch five lines ; from which the shaft 



* Aimales du Museum, t. xiii, pi. 31. f Nova Acta Acad. Nat. Curios., vol. XT, pt. i, T. VI. 



X lb., T. VII and VIII, 22, 23. 



