CRETACEOUS FORMATIONS. 89 



natural perforation of its upper or lateral parietes, and corresponds with the parts 

 marked a, b, T. XXVII, figs. 1 and 2. From the number of teeth contained in this 

 part, the Pter. Ciwieri presents a much closer resemblance to the Fter. longirostris, 

 (ib., fig. 1,) than to the Pter. crassirostris, (ib., fig. 2;) and, if the entire skull were 

 restored according to the proportions of the Pter. lo7igirostris, it would be twenty- 

 eight inches in length. 



But nature seems never to retain the same proportions in species that differ 

 materially in bulk. The great Diprotodon, with the dental and cranial characters of a 

 Kangaroo, does not retain the same length of hinder limbs as its living homologue ; 

 the laws of gravity forbid the saltatory mode of locomotion to a Herbivore of the bulk 

 of a Rhinoceros ; and accordingly, whilst the hind legs are shortened, the fore limbs 

 are lengthened, and both are made more robust in the Diprotodon than in the 

 Kangaroo. The change of proportions of the limbs of the Sloths is equally striking 

 in those extinct species which were too bulky to climb : e. y., the Megatherium and 

 Mylodon. We may therefore infer, with a high degree of probability, when a longi- 

 rostral Pterodactyle much surpassed in bulk the species so called "par excellence," 

 that the same proportions were not maintained in the length of the jaws, and that the 

 species to which the fine fragment, (T. XXVIII, fig. 1,) belonged, far as it has exceeded 

 our previous ideas of the bulk of a flying reptile, did not sustain and carry thx'ough the 

 air a head of 2 feet 4 inches in length, or double the size of that of the Pelican. We 

 see, in fact, that the size of the teeth was not increased in the ratio of that of the 

 jaws. 



Although the fractured hinder part of the jaw shows no trace of the commence- 

 ment of the wide nasal aperture, there is a plain indication that the jaws w^ere less 

 prolonged than in the Pt. longirostris, in the more rapid increase of the depth of the 

 jaw. Opposite the ninth tooth, e. g., the depth of the jaw equals two fifths of the 

 length of the jaw in advance of that tooth, whilst in the Pt. longirostris it is only 

 two sevenths. The contour of the upper border of the jaw in the Pterodactylus 

 Cuvieri differs from that in both the Pt. longirostris, Pt. crassirostris, and Pt. Gemmingi, 

 in sinking more suddenly opposite the ninth, eighth, and seventh teeth, than along the 

 more advanced part of the jaw — a character which, while it affords a good specific 

 distinction from any of those species, indicates the hinder parts of the head, that 

 are wanting in the present specimens, to have been shorter, but relatively much deeper, 

 than in the Pt. longirostris. 



The first pair of alveoli (figs. 1 and 4, «) almost meet at the anterior extremity of the 

 jaw, (T. XXVIII, fig. 3,) and their outlet is directed obliquely forwards and downwards ; 

 the obtuse end of the premaxillary above those alveoli is about two lines across. The 

 palate, (ib., fig. 4,) quickly expands to a width of three lines between the second 

 alveoli, then to a width of four lines between the fourth alveoli ; and more gradually, 

 after the ninth alveoli, to a width of six lines between the eleventh alveoli, a! : here 

 the palate appears to have been slightly crushed ; but in the rest of its extent it 



12 



