CRETACEOUS FORMATIONS. 95 



Several portions of long bones figured in T. XXXI, may well belong, by their size, 

 to the same species as the portion of jaws, figs. 1 and 2, in the same plate : two of 

 them, figs, 1 1 and 12, are from a different locality, Hailing pit, but from the same 

 formation — the Middle Chalk of Kent. As all these fragments, however, consist only 

 of the simple hollow shaft, I shall proceed with the description of the better preserved 

 specimens from the chalk which are referable to the genus Pterodacti/lus. 



Pterodactylus compressirostris, Owen. Tab. XXVII, figs. 8, 9, and 10. 



This species is represented by two portions of the upper jaw, obtained from the 

 Middle Chalk of Kent, the hinder and larger of which includes the beginning of the 

 external nostril, (fig. 8, n.) The depth of the jaw at this part is 14 lines, whence 

 it gradually decreases, so as, at a distance of 3 inches in advance of this, to present 

 a depth of 10 lines, indicating a jaw as long and slender as in the Pterodactylus 

 longirostris, supposing the same degree of convergence of the straight outlines of the 

 upper and alveolar borders of the jaw to have been preserved to its anterior end : 

 that this was actually the case is rendered most probable by the proportions of the 

 smaller anterior part of the jaw, (T. XXVIII, fig. 8' and 9',) obtained from the same pit, 

 if not from the same block of Chalk, and which, with a vertical depth of 7 lines at its 

 hinder part, decreases to one of G lines in an extent of 1^ inch in advance of that 

 part. The sides of the jaw as they rise from the alveolar border incline a little 

 outwards before they converge to meet at the upper border. This gives a very 

 narrow ovoid section at the fore part of the larger fragment (fig. 9*), the greatest 

 diameter, at its lower half, being 4 lines, and the sides meeting above at a slightly 

 obtuse ridge. This very gradually widens as the jaw recedes backwards, where the 

 entireness of the walls of the smoothly convex upper part of the jaw proves that 

 the narrowness of that part is not due to accidental crushing. Had that been the 

 case, the thin parietes arching above from one side to the other would have been 

 cracked. The only evidence of the compression to which the deep sides of the jaw 

 have been subject is seen in the bending in of the wall above the alveoli, close to 

 the upper ridge, at the fore part of the fragment, in the crushed state of the palate 

 at that part, and in a slight depression of the left side of the jaw anterior to the 

 nostril. 



In an extent of alveolar border of 3^ inches, there are eleven sockets, the anterior 

 one on the right side retaining the fractured base of a tooth : the alveoli are separated 

 by intervals of about one and a half times their own diameter ; their outlets are 

 elliptical, and indicate the compressed form of the teeth : they are about 2 lines in 

 long diameter, at the fore part of this fragment, but diminish as they are placed 

 more backwards, the last two being developed beneath the external nostril. 



