32 



Pt. Cuvien, I proceed to the description of the distinct species, for 

 which I propose the name of Pterodactylus compressirostris. 



Pterodactylus compressirostris, Owen. 

 (Reptilia, PI. V. figs. 1, 2 & 3.) 



This species is represented by two portions of the upper jaw, ob- 

 tained from the Middle Chalk of Kent, the hinder and larger of which 

 includes the beginning of the external nostril (figs. 1 & 2, w). The 

 depth of the jaw at this part is fourteen lines, whence it gradually de- 

 creases to a depth of ten lines at a distance of three inches in advance 

 of this, indicating a jaw as long and slender as in the Pt. 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 pro- 

 bable by the proportions of the smaller anterior part of the jaw (figs. 

 1', 2', 3'), obtained from the same pit, if not from the same block of 

 chalk, and which, with a vertical depth of seven lines at its hinder 

 part, decreases to one of six lines in an extent of one inch and a half 

 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. 2), the greatest diameter at its 

 lower half being four lines, and the sides meeting above at a slightly 

 obtuse ridge. This very gradually widens as the jaw recedes back- 

 wards, 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 arch- 

 ing 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 an extent of alveolar border of three and a half inches there are 

 eleven sockets, the anterior one on the right side retaining the frac- 

 tured 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 two 

 lines in long diameter at the fore part of this fragment, but diminish 

 as they are placed more backwards, the last two being developed be- 

 neath the external nostril. The bony palate is extremely narrow, and 

 presents in the larger portion (fig. 3) a median smooth convex rising 

 between two longitudinal channels, which are bounded externally by 

 the inner wall of the alveolar border. There is no trace of a median 

 suture in the longitudinal convexity. The breadth of the palate at the 

 back part of the fragment is eight lines ; at the fore part it has gra- 

 dually contracted to less than three lines, but it is somewhat crushed 

 here. The naso-palatine aperture, p, commences about half a line in 

 advance of the external nostril, three inches behind the fore part of 

 the larger portion (fig. 3) of the upper jaw ; which exemplifies the 

 characteristic extent of the imperforate bony palate fonned by the 



