CRETACEOUS FORMATIONS. 91 



Pterodactylus giganteus, Bowerhanh. Tab. XXXI. 



Pterodactylus giganteus. Bowerhanh. Proceedings of the Geological Society, May 14, 



1845; in the 'Quarterly Journal of the Geological 

 Society,' February, 1846. 

 — coNiROSTBis. Oioen. DLxon's ' Geology and Fossils of the Tertiary 



and Cretaceous Formations of Sussex,' 4to, p. 401, 

 T. XXXVIII. 



This specimen consists of the upper jaw, as far as the commencement of the 

 nostril, (T. XXXI, fig. 2, n^ with the corresponding part of the lower jaw. The upper 

 jaw is a subcompressed, three-sided cone, with a more obtuse apex than in Ptero- 

 dactylus Cuvieri, and more rapidly and regularly increasing in depth as it approaches 

 the nostrils, the sides converging at an acute angle as they ascend from the 

 alveolar border, arching over the apex of the jaw, but meeting within an inch from 

 this part at a ridge, which is rather more obtuse than that in Pt. Cuvieri, and 

 formed at a somewhat less acute angle, (figs. 3 and 4.) The surface of the bone 

 appears naturally to have been less even or level than in the larger species, and 

 the thin osseous plate is similarly fissured and cracked. The part appears, however, 

 to have suffered little compression ; the palate, where it is exposed at the back part 

 of the jaw, being entire, and presenting a concave longitudinal channel on each side 

 of a prominent median ridge : its breadth opposite the ninth alveolus is 8 lines ; the 

 depth of the jaw at that part being 14 lines ; the breadth of the base of the jaw, there, 

 outside the alveoli, is 11 lines. The sides of the jaw are plane, but sink in a little 

 between the alveoli, where they become continuous with the palatal surface. The 

 alveolar border of the jaw is slightly convex lengthwise along its anterior third, and is 

 continued straight along the rest of its extent. There are ten pairs of alveoli in the 

 part of the upper jaw anterior to the bony nostril, the alveoli being separated by 

 intervals about equal to their own diameter. In the Pt. Cuvieri there are at least 

 twelve pairs of alveoli anterior to the nostril, and there may have been more, as there 

 are in the Pt. longirostris. In the Pt. crassirostris there are only six pairs of alveoli 

 in the corresponding part of the upper-jaw, and the fourth, fifth, and sixth, are 

 separated by intervals of thrice the diameter of the alveolus. 



Such characters as these place in a strong light the specific distinctions of the 

 Pterodactyli compared. The species under consideration exemplifies in the Cretaceous 

 epoch the crassirostral group of the older secondary Pterosauria, as the gigantic 

 Pt. compressirostris does the longirostral group ; the Pt. Cuvieri approaches nearer 

 a middle term between the two types of the groups in question. The length of the 

 jaw anterior to the nostril in the Pt. crassirostris, described by Goldfuss,* is 13 lines, 



* Nova Acta Acad. Nat. Cur., torn, xv, pt. i, p. 63. 



