24 PROCEEDINGS OF THE GEOLOGICAL society. __ [Nov. 10, 
anomalous bone is certainly the astragalus, as Cuvier determined it 
to be, and not a part of the fibula; it will also appear, I think, that 
Cuvier was right, from a morphological point of view, when he de- 
declared the tibia to be laterally compressed, and that there is no 
proof, but rather a presumption the other way, as to the plantigrade 
character of Lelaps. Finally, I shall bring forward evidence to 
show that the structure of the tibia aud astragalus in question ob- 
tained in all the genera mentioned, so that the groups of Orthopoda 
and Gontopoda must be disestablished. 
Prof. Cope * gave an account of the extinct reptiles which ap- 
proached the birds. ‘ He said that their approximation appeared to 
be at two points, the first by the Pterosauria, to which the modified 
bird Archwopteryx presented points of affinity. The second, and 
one not less striking, is by the Dinosauria of the orders Gonto- 
poda and Symphopoda. He showed the essential differences be- 
tween the ordinary Dinosauria and the birds to consist in the dis- 
tinct tarsal bones in two series, the anteriorly directed pubes, and 
the presence of teeth, of the first class. In the genus Lelaps 
(Cope), type of the Goniopoda, the proximal series of the tarsal 
bones was principally represented by one large astragaloid piece, 
which had avery extensive motion on those of the second series. 
This was immovably bound to and embraced the tibia, and was 
perhaps continuous with the fibula, much resembling the structure 
of the foot of the chick of the ninth day, as given by Gegenbaur. 
The zygomatic arch was of a very light description. He was con- 
vineed that the most bird-like of the tracks of the Connecticut 
sandstone were made by a nearly allied genus, the Bathyqnathus 
(Leidy). These creatures, no doubt, assumed a more or less erect 
position, and the weight of the viscera &c. was supported by the 
slender and dense pubic bones, which were to some extent analo- 
gous to the marsupial bones of implacental Mammalia, though 
probably not homologous with them. 
“ He said he was satisfied that the so-called clavicles of Zquanodon 
and other Dinosauria were pubes, having a position similar to 
those of the Crocodilia—also that a species of Lelaps had been 
observed in France, by Cuvier, which was different from the L. 
aquilunguis, and which he proposed should be called Lelaps gal- 
heus. 
“* Compsognathus (Wagner), type of the Symphopoda, expressed 
the characters of the latter in the entire union of the tibia and fibula 
with the first series of tarsal bones—a feature formerly supposed to 
belong to the class Aves alone, until pointed out by Gegenbaur. 
This genus also offered an approach to birds in the transverse 
direction of the pubes (unless this be due to distortion in the speci- 
men figured by Wagner), their position being intermediate be- 
tween the position in most reptiles and in birds. Other bird-like 
* Proceedings of the Academy of Natural Sciences, Philadelphia, Dec. 31st, 
1867. I may remark that my memoir “On the Classification of Birds” was 
published in the summer of 1867 in the ‘ Proceedings of the Zoological Society.’ 
Prof. Cope has evidently done me the honour to study it carefully. 
