164 
PEOFESSOE OWEX OX THE TEETEBEAE 
The cervical vertebrae average seven in number, counting the coalesced atlas and axis 
as one. They are characterized by their superior size, and especially length, as com- 
pared vrith the other vertebrae in the same skeleton ; but diffei’ in different species in this 
respect, being longest in those Pterodactyles with long, light and slender jaws, shortest 
in those with shorter, stronger and thicker jaws. The. third to the sixth inclusive pre- 
serve the same, or nearly the same, length ; the seventh becomes shorter, and exhibits 
other modifications transitional to the dorsal vertebrae. 
The ordinary cervical vertebra in Pterodactylus Sedgimclcii (figs. 1—10) has a long 
depressed centrum {h-c) coalesced with the neural arch (w), slightly concave lengthwise 
at the sides, slightly convex lengthwise below, at least in the fourth or fifth cervical 
(fig. 6). It developes a pair of short obtuse processes (y)'}, which form the posterior 
inferior angles, and between these the under surface is concave transversely; the airicular 
ball {h) seems as if tilted up above the level of these processes. There is a low obtuse 
hypapophysis (A) at the fore-part, the base of which is in some cerricals prolonged 
backward a short way as a rudimental ridge. A large ‘ foramen pneumaticum’ (figs. 5. 
7, 8, o) perforates the middle of the side of the vertebra at the line of junction of the 
centrum and neural arch ; it conducts chiefly to the large cancelli in the centrum. 
The neural arch is low ; broader, but shorter, than the centrum. Viewed from above 
(fig. 9), it presents a subquadrate form, deeply emarginate before and behind, less con- 
cave at the sides, and with the four angles produced to form the zygapophyses. The 
articular surfaces of the anterior pair (z) look upward, inward and forward ; those of 
the posterior pair (z') downward, outward and backward : both are flat. The anterior 
zygapophyses (fig. 10, z) project on a level with the sides of the anterior articular cup. 
some way in advance of it, the base of the process being dirided by an oblique notch 
from the cavity. The posterior zygapophyses (fig. 7, z') do not extend quite to the 
hinder ball; they project above its level; there is a tuberosity (m) above the articular 
smfface in many vertebrse. The neural canal (fig. 6, n) is shghtly expanded at its outlets, 
sub cylindrical in transverse section, about half the length of the centrum ; consequenth 
leaving a large proportion of the spinal cord unprotected by bone at the intervals of the 
successive neural arches. The neural spine (fig. 8, ns) is moderately produced, com- 
pressed and truncate ; its base is coextensive with the summit of the ai’ch, and it con- 
tracts as it rises, with a sharp anterior border. Not any of the cerrical vertebrae possess 
the pleural elements which give the great transverse anterior breadth to the cerricals 
in the’ bird, and complete there the large vertebrarterial foramen on each side : nor is 
the hypapophysis double, forming a transverse pair, as in most of the neck-vertebins of 
birds. The processes answering to p' in the Pterodactyle are rudimental, when present- 
in the bird. 
The chief differences in seemingly answerable cervical vertebrae, in different indi- 
viduals, perhaps species, of large Pterodactyles from the Upper Greensand, ai'e seen in 
the degree of depth or depression of the centrum, with corresponding differences in the 
