CHAEACTEES OF THE OEDEE PTEEOSAUEIA. 
165 
form of the foramen pneumaticum, as shown in figs. 5, 7 and 8 ; with some slight differ- 
ences in the hypapophysis affecting the lower contour of the centrum, and in the propor- 
tions of the articular surfaces of the zygapophyses. 
In the sixth cervical vertebra the centrum becomes flatter below, and an anterior par- 
apophysis (j?) sometimes extends to the under part of the prezygapophysis (z), circum- 
scribing a small arterial foramen, as in fig. 11. 
In the last cervical (fig. 12) the centrum becomes much shorter : a diapophysis (d) is 
more distinctly developed behind the prezygapophysis (z), and these, with the parapo- 
physis now completing a larger arterial canal, form a protuberance resembling that in 
the bird, on each side the fore-part of the vertebra. 
In the dorsal vertebrae (figs. 13-21) the centrums grow deeper as they shorten, with 
a proportionate expansion of the articular cup, as in fig. 17, and ball, fig. 20. The 
posterior zygapophyses (fig. 14, z') are more approximated, project from a higher level, 
are shorter, with the articular surfaces rather convex and looking more outward, and 
more distinct from the tubercle above (fig. 15, z', m!). The neural spine {ns) is thicker. 
There is a small pneumatic foramen behind the base of each diapophysis. The walls of 
the neural arch increase in height, expanding as they rise, to send out the diapophyses {d) 
to which the free ribs articulate. These ribs are slender and hollow, as in Serpents 
(fig. 23, a). 
In what appears to be a lumbar vertebra (fig. 24) the neural arch again sinks, and the 
strong diapophysis (fig. 24, d) projects far, without supporting a rib. In the first sacral 
vertebra (fig. 25) the fore-part of the neural arch {d) forms a broad transversely extended 
vertical wall above the small neural canal {n), and the strong transverse process [d..p) 
sinks or extends its base vertically down to the lower border of the inferiorly flattened 
centrum (fig. 25, c and fig. 26, c). Fig. 27 shows parts of the bodies of three anchylosed 
sacral vertebrae of a neocomian Pterodactyle, the first having an anterior concave articula- 
tion {ih. a), as in the larger specimen, fig. 25 ; the groove for the passage of the nerve 
notches the back part of the parapophysis close to the line of suture with the second 
sacral vertebra. In this vertebra' the corresponding nerve-notch is more advanced, 
leaving a short sutural surface behind, indicative of a position of the neural arch crossing 
for a short extent the line of junction of the second with the third sacral centrum. The 
parapophyses (^) of the second vertebra are sent off almost on a level with the lower 
surface of the centrum, which is almost flat. 
Atlas and axis vertebrce of the Pterodactyle (figs. 28-34). 
These vertebrae early coalesce with each other, but I have been able to separate them 
in a young specimen. 
The atlas consists of a centrum (figs. 28, 29,30, c) and of two styliform neurapophyses 
(ib. no)-, in one specimen there seemed also to be a very small flattened neural spine. 
The centrum is so short as to be discoid : it is flat where it joins and becomes anchylosed 
to the axis, and is concave for the occipital tubercle: this cup is circular (fig. 28, c). 
