TRANSACTIONS OF THE SECTIONS. 99 
of fragmentary remains of Pterodactyles which had been discovered in the Upper 
ees formations, now extensively worked for phosphatic nodules, near Cam- 
ridge. 
Among these were many more or less entire vertebrae demonstrating their pro- 
ceelian type, as in modern Lizards; the Pterodactyles being the earliest known ver- 
tebrate animals with ‘ cup-and-ball’ vertebra, and with the ‘cup’ at the fore-part of 
the centrum. ‘The atlas consists of a centrum, two slender styliform neurapophyses, 
and a neural spine, which is small and discoid. The centrum is a thin disc; flat 
where it joins, and becomes anchy losed to, the axis; concave for the occipital tubercle. 
The neurapophyses, resting on the upper part of the sides of the centrum of the atlas, 
converge and articulate above with two tubercles on the fore-part of the neural arch 
of the axis. The centrum of the axis is 8 lines longer than that of the atlas, which 
was one line long in the specimen described. It expands posteriorly, where it ter- 
minates, below, in a pair of short obtuse apophyses, above which is the convexity 
for articulating with the third vertebra. At the middle of the under surface is a low 
hypapophysial ridge. At the middle of the side of the centrum is the large pneu- 
matic foramen. The neural arch is anchylosed with the centrum, and sends off 
from each posterior angle the zygapophysis, which has a tubercle above and a flat 
articular surface below looking downward, and a little outward and backward. The 
neural canal expands at the posterior outlet. The neural spine is broken away. 
In the ordinary neck-vertebre the centrum is oblong and subdepressed, slightly 
compressed at the middle, subcarinate at the fore-part of the under surface, the back 
part of which expands and is slightly produced into a short thick obtuse process on 
each side. The anterior concavity is a long transverse oval ; beneath which, in most, 
is a tuberosity terminating there the median keel. The posterior ball has a similar 
transversely extended elliptical figure—the characteristic of the neck-vertebre of the 
Pterodactyle, but tilted up by the curve of the under surface of the centrum, above 
the level of the two terminal tuberous processes. A large pneumatic foramen, of an 
elliptic form, opens upon the middle of each side of the centrum close to the anchy- 
losed base of the neurapophysis. The texture of the centrum presents a few very 
large cancelli, which doubtless received the air from the cervical air-cells. The sur- 
face of the centrum is formed by a very thin compact layer of bone, a little thicker 
where it forms the articular cup. 
The neural arch, between the notches for the nerve-outlets, is not quite two-thirds 
the length of the centrum; the hinder notch is the deepest ; the arch is low and 
broad, less concave on each side than it is before and behind, with the four angles 
rather produced, and supporting the articular surfaces, of which the two anterior 
look upward and forward, the two posterior downward and backward. The sides of 
the arch extend outward so as to overhang those of the centrum. The posterior 
zygapophyses do not extend so far back as the articular ball of the centrum. 
At the base of the neck, or beginning of the back, the vertebrae suddenly decrease 
in length ; the hypapophysis disappears, or is represented only by a slight production 
of the lower border of the anterior cup; the parapophyses are less produced, the 
lower surface of the centrum is flattened, and presents a quadrate form. There is 
now a considerable development from the fore-part of each side of the neural arch 
and contiguous part of the centrum, and thereby the last cervical or first dorsal ver- 
tebra of the Pterodactyle more resembles the corresponding vertebra of the bird. 
The parapophysis, diapophysis, and rudimental rib coalesce around the vertebrarterial 
foramen ; an oblique ridge is continued from the upper border of the anterior arti- 
cular cup upon the parapophysis ; a parallel oblique ridge is continued from the an- 
terior zygapophysis downward and outward upon the pleurapophysis; the diapo- 
physis makes a low obtuse projection above the pleurapophysis and behind the 
zygapophysis. Above these developments the neural arch contracts from before 
backward, to an extent of 5 lines, as compared with a total vertebral breadth, ante- 
riorly, of 1 inch 8 lines; it then rapidly expands, rising vertically at its fore part, 
and developing at its back part the posterior zygapophyses, the articular facets of 
which look more directly outward than in the long cervical vertebre ; the superin- 
cumbent tubercle is more distinct from the facet; the posterior zygapophyses are 
also much more approximated than in those vertebre; they are separated behind 
by a semicircular concavity; the base of the neural spine in the martina here 
