CHAEACTEES OF THE OEDEE PTEEOSAUEIA. 
163 
with respect to the cervical and dorso-lumbar vertebrae, the terminal articular surfaces 
of the vertebral bodies are simply concave anteriorly (Plate X. fig. 1), convex posteriorly 
{ih. fig. 2)*; and that they consequently manifest the earliest known instance of the 
‘procoehan’ type which now prevails in the reptilian class. But in no other reptile are 
those articular surfaces so narrow vertically in proportion to their breadth as they are 
in the cervical vertebrse of the Pterosauria [ih. figs. 1, 2, 12-14, 5, c ) : in the dorsal 
series the cup and ball present more ordinary saurian proportions. 
This fact, being estabhshed, will give new and increased interest to the working out 
and examination of any detached vertebrae from secondary rocks which resemble in 
texture and size those of Birds and Pterodactyles. It has been alleged, for example, 
on microscopic characters of the osseous tissue, that certain pneumatic wing-bones found 
fossil in Stonesfield slate, are those of birds. But every such vertebra from that lower 
oolitic bed which I have yet seen, has the simple terminal articular concavity or convexity 
characteristic of the Pterodactyle. A single specimen showing the interlocking joint, 
i. e. a transverse concavity and vertical convexity, or the reverse, would establish the fact of 
the existence of birds during the period of deposition of the stratum containing such 
fossil vertebra. There is but one exception, so far as I know, in the whole class of 
birds, to the foregoing type of vertebral structure ; this occurs in a bird {Aptenodytes) 
which does not fly, but has the wing-bones dense, solid, and modified in form to serve 
the ofiice of a fin, and is exemplified in but a small part of the vertebral column. In 
the third to the eighth dorsal vertebrse inclusive, the fore-part of the centrum is simply 
convex {ih. fig. 22, c), the hind part concave, and this part is concave in the second 
dorsal ; but the fore-part of this dorsal vertebra is concavo-convex, as in the cervical 
vertebrae of the Penguin, and in the* cervico-dorsal vertebrae of all other birds. But, 
besides the reverse positions of the cup and ball in the above dorsal vertebrae of the 
Penguin, as compared with the dorsal vertebrae of the Pterodactyle, the latter might be 
distinguished by the absence of the large bifurcate hypapophysis {ih. fig. 22, hy) which 
projects from the dorsal vertebrae of the Penguin; the inferior surface of the dorsal 
vertebrae in the Pterodactyle being smooth and simply convex transversely, and slightly 
concave longitudinally. The anterior cup becomes more shallow in the last lumbar and 
first sacral vertebrae of the Pterodactyle ; the confluent articular surfaces of the sacral 
vertebrae are flattened. In the caudal vertebrae of the Pterodactyle the anterior trans- 
versely-elliptical cup and posterior ball are resumed at the articular end of the centrum ; 
at least in most of the anterior caudal vertebrae of the great Pterodactylus SedgwicJcii 
{ih. figs. 36, 37). 
* Von Metee was led to believe from tbe crushed specimen of Pterodactylus Gemmingi, described and 
figured in his ‘ Palseontographica,’ Erster Bd. dto. 1851, p. 10, that both articular surfaces of the bodies of 
the cervical vertebrae were concave ; and that the hinder surface of a dorsal vertebra was not convex. But 
this error was due to the state of the specimen. See also his ‘ Eeptilien aus dem Lithographischen Schiefer, 
fol. 1859, p. 68. 
