167 
CHAEACTEES OE THE OEDEE PTEEOSAUEIA. 
behind the diapophysis, and conducts to the cancellous tissue of the neural arch. Ihe 
centrum is produced into a strong hypapophysis below the posterior articular surface, 
but not expanded laterally into transverse processes, answering to those marked jj in 
the Pterodactyle. The hinder articular surface of the centrum of the axis of the bird is 
convex transversely, but concave vertically, not simply convex, as in the Pterodactyle ; 
thus a portion of the vertebra of that reptile, notwithstanding its pneumatic structure, 
might be distinguished from the vertebra of a bird. 
The caudal region of the spine is that which, in the Pterosauria, as in the Bats and 
most other natural groups, is subject to most variety. In Pterodactylus {Phamphorhyn- 
cJius) Gemmingi, v. Meter, from Solenhofen slate, the tail is very long, and most of the 
long and slender vertebrae, between thirty and forty in number, seem to have coalesced 
into a stiff style for supporting an expanded interfemoral membrane. In Pterodactyls 
longnostris, Cuv. the tail is short, and the small and short vertebrae are free. In the large 
Pterodactyles from the Cambridge Greensand, it would seem that the tail was of mode- 
rate length and the vertebrae are free. The collections examined by me included fifteen 
caudal vertebrae. 
The largest of these (figs. 35-37) measures I-| inch in length; it is slightly contracte 
in the middle ; the fore-part of the under surface is a little produced ; the back part 
almost flat between the rudimental processes (^'): the shallow anterior concavity (fig. 
36, c) has resumed its transversely elliptical shape, and the hinder convexity is define 
below by a shallow groove connecting the processes {p'). There is no pneumatic foramen, 
unless a small hole on each side the hinder outlet of the neural canal have served as such. 
The neural arch is long and low, of one piece with the centrum, whmh extends beyond 
it posteriorly ; it sends off short obtuse zygapophyses before and behind : those in front 
extend beyond the cup of the centrum ; the surfaces on those behind look downward 
and backward. The base of the spine is coextensive with the summit of the arch, but 
is narrow. The neural canal is much contracted. There is no indication of a haemal 
arch, either by articular or fractured anchylosed surfaces. The diameter of the middle 
of this vertebra is 6 lines. 
The next caudal vertebra in size measures I inch 5 lines. The base of the neural 
spine begins two lines behind the fore-part of the arch, but terminates nearer the hind 
part. The nerve-grooves notch the hinder zygapophyses. 
Three more slender caudal vertebrae present each a length of I inch 3 lines : the dia- 
meter at the middle is 5 lines in one, 4 in a second, and ^ in the third vertebra, show- 
ing that they become more slender without losing length. A caudal vertebra, 3 lines 
across the middle, appears to have been nearly an inch in length , but both extremities 
are injured. 
The most perfect vertebrae of other species of Pterodactyles from older formations 
which I have as yet had opportunities of examining, are those of a rather large species 
from the oolitic slate at Stonesfield. Dr. Buckland kindly transmitted to me, some years 
ago, two drawings of one of these vertebrae (figs. 38 and 39). They are more slender in 
