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 flexibility 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 Pterodactyim longioollum and Pt. 
longirostris ; it is least in Pt. crassirostris and Dimorphodon macronyx, and apparently 
also in Pterodactylus sinms, if we may judge by the breadth, compared with the length, of 
the vertebra figured in PI. XVIII, (figs. 1 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 Pterodactylus 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 vertebrae fell not 
below twelve in any species, nor exceeded fifteen or sixteen in Pterosauria, Pterodactylus 
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. 
1 have seen no specimen of Diniorphodon yielding definitely the number of the dorso- 
lumbar vertebrae, ^. 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 of 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 
should 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, n), testify to the strength and closeness of their reciprocal articu- 
lations, under disturbing influences which have affected 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 {Pyrgita domestica)\iSLS twelve (‘ Osteol. Catal. Coll, of Surgeons,’ No. 1571, vol. i, 
p. 297). 
2 “ 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 the body, for the purpose of oiling and cleansing the plumage.” 
— Anat. of Vertebrates' ii, p. 39. 
® Vol. cit., p. 368 : — “II semble qu’il en est reste au moins douze en place du cote gauche.” The 
specimen figured by Von Meyer, op. cit. in pi. i, fig. 1, shows thirteen ribs on the left side of the trunk. 
