250 BRITISH FOSSIL REPTILES. 



The bony palate is extremely narrow, and presents, in the larger portion, fig. 10, 

 a median smooth convex rising between two longitudinal channels, which are bounded 

 externally by the inner wall of the alveolar borders. 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 8 lines, at the fore part it has gradually contracted to less than 3 lines, 

 but it is somewhat crushed here, (fig. 10, a.) The naso-palatine aperture commences 

 about half a line in advance of the external nostril, 3 inches behind the fore part of 

 the larger portion of the skull : its form and extent, so far as it is preserved, are 

 accurately shown in fig. \0,p, and it well exemplifies, in this specimen, the charac- 

 teristic extent of the imperforate bony palate formed by the long single premaxillary 

 bone in the present order of Saurians. 



The fragment from the more advanced part of the jaw, fig. 8, contains five pairs 

 of alveoli, in an extent of 2 inches, these alveoli being rather larger and closer 

 together than in the hinder part of the jaW; Owing to the compression which the 

 present portion has undergone, the orifices of the alveoli are turned outwards ; the 

 bony palate being pressed down between the two rows, and showing, probably as 

 the result of that pressure, a median groove between two longitudinal convex ridges ; 

 but the bone is entire and imperforate. The form of the upper jaw in the present 

 remarkable species diifers widely fi'om that of the two previously described specimens 

 from the Chalk, in its much greater elongation, its greater narrowness, and from 

 the Pi. Cuvieri, more especially, in the straight course of the upper border of the 

 jaw, as it gradually converges towards the straight lower border in advancing to the 

 anterior end of the jaw. The alveoli, and consequently the teeth, are relatively smaller 

 in proportion to the depth of the jaw than in the Pt. Cuvieri, and are more numerous 

 than in the Pt. (jiyanteus : they are, probably, also, more numerous than in the 

 Ft Cuvieri; although, as the whole extent of the jaw anterior to the nostril is not 

 yet known in that species, it would be premature to express a decided opinion on 

 that point. As we may reasonably calculate from the fragments preserved, 

 (PI. 3, figs. 8 and 8',) that the jaw of the Pterodactylus compressirostris extended 

 seven inches in front of the nostril, it could not have contained less than twenty 

 pairs of alveoli, according to the number and arrangement of those in the two 

 portions preserved. 



The osseous walls in both portions present the characteristic compactness and 

 extreme thinness of the genus : the fine longitudinal striae of the outer surface are 

 more continuous than in the Pt. Cuvieri, in which they seem to be produced by a 

 succession of fine vascular orifices produced into grooves. The conspicuous vascular 

 orifices are almost all confined to the vicinity of the alveoli in the Pt. compressi- 

 rostris. This species belongs more decidedly than the Pt. Cuvieri to the longi- 

 rostral section of the Fterosauria : whether it had an edentulous prolongation of the 

 fore part of the upper and lower jaw, as in the Ft. Gemminffi, remains to be proved. 



