LIASSIC FORMATIONS. 



67 



tians have fewer definite cervicals ; Birds have more. I have not seen any Bird with fewer 

 than eleven cervicals.^ The length and flexibihty of the neck is correlated with the covering 

 necessitated by the high temperature of the Bird." The cold-blooded flying Reptiles 

 have a comparatively short and rigid neck, but of a thickness and strength proportionate 

 to the size of the head, and adequate to the work to be performed by the jaws in over- 

 coming and bearing away the prey they may have seized. 



The chief variety manifested by the Pterosauria in the cervical region is in the relative 

 length of the last six vertebrae ; this is greatest in Pterodactylus longicollum and Pt. 

 hngirostris ; it is least in Pt. crassirostris and Dimorphodon macronyx, and apparently 

 also in Pterodactylus sunns, if we may judge by the breadth, compared with the length, of 

 the vertebra figured in PI. XVIII, (figs. I and 2) of my Monograph, above cited, of 1860. 



There seems to have prevailed a greater range of variety in the number of vertebrae 

 between the cervical series and the sacrum. In Plerodadylm lonyirostris, Cuvier esti- 

 mated at least twelve which supported moveable ribs,^ and nineteen or twenty in the 

 dorso-lumbar series. Von Meyer concluded that the number of dorsal vertebra) fell not 

 below twelve in any species, nor exceeded fifteen or sixteen in Pterosauria, Pterodadylus 

 Kochii shows fourteen dorsal vertebrae ; Pt. crassirostris not more than twelve, reckoned 

 by the number of pairs of free ribs, which can be satisfactorily discerned. 



I have seen no specimen of Dimorphodon yielding definitely the number of the dorso- 

 lumbar vertebrae, i. e. of the vertebrae between the cervical and sacral ; it is from the best 

 considerations I have been able to give to the analogies of these vertebral formulae, in better 

 preserved examples of other species ^Pterosauria, that I assign thirteen to this series in 

 my restoration of Dimorphodon macronyx (PI. XX) ; and I conclude that the thirteenth 

 was a true lumbar vertebra or without connection with a free pair of ribs. If there 

 shoidd prove to be error in this estimate I cannot think it will extend beyond one vertebra, 

 or at most two, in excess of twelve dorsals. 



The nine dorsal vertebrae, which have kept together, in almost a straight line, in the 

 specimen (PI. XVIII, d), testify to the strength and closeness of their reciprocal articu- 

 lations, under disturbing influences which have afiected so great and general a degree o^ 

 dislocation of most other parts of the skeleton. 



BucKLAND seems first to have observed the convexity of one of the terminal articular 

 surfaces of the centrum of a dorsal vertebra, and to have deduced an affinity therefrom ; 



' The Sparrow {Pt/rffita domestica) has twelve (' Osteol. Catal. Coil, of Surgeons,' No. 1.t"1, vol. i, 

 p. 297). 



- " As the prehensile functions of the hand are transferred to the beak, so those of the arm are per- 

 formed by the neck of the Bird ; that portion of the spine is, therefore, composed of numerous, elongated, 

 and freely moveable vertebrae, and is never so short or so rigid but that it can be made to apply the beak to 

 the coccygeal oil-gland, and to every part of tlie body, for the purpose of oiling and cleansing the plumage." 

 — ' Jnat. of Vertebrates,'' ii, p. 39. 



^ Vol. cit., p. 368 : — "II semble qu'il en est reste au moins douze en place du coto gauche." The 

 specimen figured by Von Meyek, op. cit. in pi. i, fig. 1, shows thirteen ribs ou the left side of the trunk. 



