328 Mr. H.Seeley on the Avian Affinities of Pterodactyles. 
may look at a glance, the wings of birds and Pterodactyles do 
not differ in kind, but only in degree. The plan is the same, 
but the modifications of it are different. And these divergences 
seem chiefly to have reference to the fact that Pterodactyles 
were quadrupeds; whence it comes that while in birds the whole 
limb is modified for flight, the whole limb in Pterodactyles, ex- 
cepting one finger, is also modified for standing. And thus it 
happens that in birds the bones of the arm and forearm are 
enormously long, while in Pterodactyles they are comparatively 
short, and that, while in Pterodactyles the phalanges of one 
finger are enormously elongated to form a wing, in birds, where 
they have no such function, they are short. 
Therefore I affirm that the fore imb of Pterodactyles has no- 
thing reptilian in its mode of construction, but is essentially 
avian in type; and even if it should be found that the wing- 
finger supported a membranous wing, which there are no suffi- 
cient reasons for assuming as certain, that would rather show 
an approximation towards mammals than the faintest affinity 
with the Reptilia. 
Then the form of body and proportions of its parts are worth 
remark in Pterodactyles ; for they find no parallel among the 
Reptilia, but are very bird-like. The large, long head, tapering 
in front, is essentially the head of the bird in form, and proba- 
bly, but for the teeth, would have been always so regarded. 
Although Plesiosaurs and turtles both have long necks, the 
proportions of the neck in Pterodactyles are decidedly those of a 
bird. The length of the limbs finds its parallel in no group of 
reptiles, but is characteristic of birds ; and the proportions and 
form of the breast-bone are only to be matched among birds. 
Neither the length of the tail in some tribes nor its shortness in 
others is opposed to our knowledge of the structure in birds. 
Therefore it is not astonishing to find that Blumenbach con- 
sidered the Pterodactyles to be birds, that Sémmering named 
the genus Ornithocephalus, or that Prof. Hermann placed it be- 
tween the birds and mammals. 
I will now briefly give some of the results of a consideration 
of the several bones. And here, no more than in the organiza- 
tion, do I find any characteristics of reptiles, or anything to 
make me doubt that the Pterodactyles were, even in the details 
of structure, formed essentially on the ormithic plan. 
If the reader will refer to any figure of the skull of a Ptero- 
dactyle, and compare with it any similarly formed skull of a bird 
(say that of the heron), it will be found that the form and size 
of the region for the brain is the same in both, and that all the 
cavities of the skull, orbits, nares, and the apertures between 
them, correspond exactly in the two. The eye is usually more 
