98 FOSSIL REPTILIA OF THE 



preserved end is shown at fig. 2*, where a and h may give the form and position 

 of natural articular surfaces, but there seems to have been some slight restoration 

 here : <? is a vacuity where the bone is deficient : the contour of the border of the bone 

 at a, fig. 2, which is obviously entire, satisfactorily indicates, however, the concavity 

 of the articular surface as shown at a. This, were the bone an ulna or a phalanx of 

 the wing-finger, would determine the end to be a proximal one : but if the bone were 

 a radius, the concavities a and h might be adapted to some of the small carpal bones. 

 The presence of a pneumatic foramen, at p, figs. 1 and 3, would seem, however, to 

 show the extremity near which it is situated to be a proximal one, and if any trust could 

 be placed in the analogy of the bones of birds, the position of this pneumatic foramen, 

 with the double articular concavity, a and h, and the three-sided shape of the shaft, 

 would concur in leading to a reference of the bone to the ulna. 



The side of the expanded proximal end shown in fig. 2 is slightly convex : that 

 shown in fig. 1 is almost flat, whilst the pneumatic foramen is situated in a deep and 

 narrow concavity or groove which forms the beginning, or the end, of the narrowest 

 of the three sides of the shaft of the bone. But the concavity is speedily changed, 

 as it passes down the shaft, for a convexity, which subsides to a flattened surface at 

 the middle of the shaft, as shown in fig. 2, The broadest side, shown in fig. 2, 

 becomes flattened in the shaft of the bone : tlie transverse section of which, four 

 inches from the entire end, is shown in fig. 3*, which also gives the thickness of the 

 compact osseous walls of the large air-cavity of the shaft ; the thickness of these walls 

 is also shown at their fractured borders in figs. 1, 2, and 3 ; it exceeds, as might be 

 expected, that of the similarly sized pneumatic wing-bones of the gigantic Crane and 

 Pelican. The character of the surface of the bone closely resembles that of the portion 

 of the jaw of the Pterodad^lus Cuvieri. 



Long Bones of Pterodactylus compressirostris. Tabs. XXIV, XXX, 



figs. 4 and 5. 



In the reference of the long bones from the same locality or division of the Chalk 

 Formations as those from which the jaw-bones of the Pterodactyles have been derived, 

 the chief guide, at present, is the relative size of the parts. 



It is not likely that one can err in associating the largest specimens of the 

 wing-bones, such as that above described, to the Pterodactyle, with the largest and 

 strongest jaw, especially when we find the same fine furrows and foramina giving a silky 

 appearance to the surface of both. 



The smaller specimens appear by their more compact and smooth surface to belong 

 to the smaller species ; but they may have been parts of smaller or younger individuals 

 of the larger species ; this, however, is the least likely of the conjectures to which, in the 



