330 Mr. H. Seeley on the Avian Affinities of Pterodactyles. 
similar to that of a bird of flight.” And, again, the same able 
authority remarks, ‘ In the main, the Pterosaurian breast-bone, 
like the scapular arch, is formed on the ornithic type; but the 
postcoracoid lateral emarginations are distinctive Pterosaurian 
characters.” And, going into details, Prof. Owen observes, 
“Only in birds are distinct synovial articulations provided for 
the coracoids, which, in the main, are situated and shaped as 
in the Pterodactyle.’” After so clear an exposition, I cannot 
draw the conclusion that, because the Pterodactyle has the 
characters of a bird, therefore it must be a reptile. 
The compact pelvic bones are distinctive. The femur, tibia, 
fibula, and humerus are in the main avian. Nor will any of the 
remaining bones be found to show reptilian characters. From 
facts such as these it seems to me no hard task to determine 
whether the Pterodactyle has the organization of a reptile or of 
a bird. I find it in every essential principle to be formed on 
the avian plan. Yet it differs more from existing birds than 
they do among themselves, and therefore cannot be included as 
an order of Aves; for the poimts of structure in which it differs 
from birds are those in which all existing birds agree. I there- 
fore regard it as forming a group of equal value with Aves, each 
as a subclass, forming together a great class of birds. Its dis- 
tinctive characters are—in having teeth, in the simple convex or 
concave articulation of the vertebra, in the separate condition 
of the tarsal and metatarsal bones, in having three bones in the 
forearm instead of two, in a peculiar carpal bone, in the sacrum 
formed of few vertebre, and in the modification of the wing by the 
enormous development of the phalanges of one finger. The sub- 
class so characterized forms a parallel group with the true birds. 
Whether it may not in some points of organization rise above 
birds, is a question on which IJ offer no opinion, further than to state 
that in none of the typical mammalian characters does it approach - 
the mammals. Reptiles, as may naturally be expected, resemble 
the Pterodactyles, because the gap between reptiles and birds is 
smaller, and the osteological correspondences between them are 
many. Hence those parts in which the Pterodactyle falls short 
of the specialized characteristics of true birds may rightly be 
regarded as those in which it is more Saurian. Such are the 
quadruped motion, the lizard-like hand, the simple articulation 
of the vertebree, the smaller sacrum and less-developed pelvic 
bones, the divided condition of the tarsals and metatarsals, the 
succession of the teeth, and the often long tail. But, while 
making it more Saurian, they do not necessarily imply that the 
animal was more reptilian in the sense of being of lower organi- 
zation, but only that it diverged less from the Saurian type on 
which the osteology of the bird seems founded. Therefore the 
