Mr. H. Seeley on the Avian Affinities of Pterodactyles. 329 
developed in the Pterodactyle than in birds, is similarly defended 
with sclerotic plates, and, as a result of larger size no less than 
of the greater intensity of life im the animal, it is surrounded 
with bone. The lachrymal, similar to that of a bird, grows 
down from above, and meets a process of the jugal, of which 
there is a trace in some birds, which grows up from below. 
Then the eye extends down to the quadrato-jugal, which accord- 
ingly is much thickened, and appears to extend up the inner 
side of the quadrate bone (from which it sometimes cannot be 
separated) to meet the outward process of the alisphenoid and 
squamosal bones. This slight and evidently functional differ- 
ence is almost the only important deviation from the bird-type 
seen in the Pterodactyle skull. . As I have already remarked, 
the quadrate bone, both in form and in its relations to the skull, 
is quite the same as that of a bird; and the articulation with the 
lower jaw is exactly matched by the complex articulation of 
some birds. ‘The relations and proportions of the premaxillary, 
maxillary, and nasal bones are those of birds; and, as far as 
can be judged from figures, the other bones of the skull are not 
less avian. As regards Cambridge specimens, I can confidently 
say that, if seen separately, and their history were unknown, no 
anatomist would ever dream of their being anything but a new 
tribe of birds. 
The vertebral column of true birds is very peculiar, and, with 
some few exceptions, is readily distinguished from that of all 
other animals by the concavo-convex articular surfaces. No 
Pterodactyle is at present known to show this character, though 
both kinds of articulation exist in the class. The Dimorphodon 
has vertebre which are convex in front, while the Pterodactyloid 
animals from the Cretaceous beds have the vertebrae concave in 
front ; hence, seeing that the development is entirely functional, 
it would not be surprising to find Pterodactyles with vertebra 
like birds ; for the bird’s vertebra might be easily modified into 
the concave or the convex type. But it would seem to be by no 
» means necessary that a bird should have this concavo-convex 
articulation to the vertebre ; for, as Prof. Owen has stated, “in 
the third to the eighth dorsal vertebree of Aptenodytes, the fore 
part is simply convex, while the hind part is concave.” Thus 
the Pterodactyle may be regarded as a case m which all the 
vertebre have a like simplicity of articulation; for in all their 
other features, from the atlas and axis downwards, they present 
characters which have been recognized by Cuvier, Owen, and other 
observers as only comparable to those of birds. In the pectoral 
apparatus every bone might have been that of a true bird, nor 
can any characters be given suflicient to distinguish them well. 
Prof. Owen remarks that “the scapular arch is remarkably 
