102 BAC/R. [Vol. I. 



The oldest Crocodiles, the Belodontidae, and Aethosauridae are 

 very much allied to the Zanclodontidae and the Sauropoda, and 

 I feel quite sure that Crocodiles and Dinosaurs converge in the 

 lower Triassic. 



The Birds, and among those the Ratitae with teeth, went 

 off from the Ornithopoda^ but not from any known form. 



Probably they started from some Ornithopoda-like form in the 

 Triassic, because I do not doubt that some of the footprints in 

 the Connecticut sandstone are made by true Birds. 



The Orthopoda and Birds are the only Sauropsida in which 

 the pubis is directed backwards ;^ a fact of great importance. 



ArcJiczopteryx is not on the direct line, but is a very much 

 specialized member of a collateral branch. 



The Theromorpha. 



Prof Cope includes the Theromorpha in the group con- 

 sisting of the Dinosauria (Crocodilia) and Ornithosauria. I can- 

 not agree with that proposition. 



The Theromorpha form a natural group, like that containing 

 the Crocodilia, Dinosauria, Ornithosauria, and Birds. They are 

 limited to the Permian and Triassic. 



This group is characterized by the absence of the postorbito- 

 squamosal arch, the presence of the entepicondylar foramen, and 

 the peculiar structure of the scapular arch. 



The Pelycosauria, including Owen's Theriodontia, form the 

 original stage, having the centra of the vertebrae notochordal and 

 the intercentra present ; the Anomodontia are very much special- 

 ized ; the centra are not notochordal, the intercentra wanting, and 

 the dentition in a rudimentary condition. Prof Cope considers 

 the Theromorpha as the ancestors of all other Reptilia with, 

 possibly, the exception of the Ichthyopterygia. He also con- 

 siders the Pelycosauria as the ancestors of the Mammalia. I 

 tried to show in a lately published paper ^ that the Theromorpha 

 are already too much specialized to be theancestors of Mammals. 



* Baur, G. Note on the Pelvis in Birds and Dinosaurs. Amer. Nat., Dec, 1884, 

 p. 1274. 



— Bemerkungen iiber das Becken der Vdgel, und Dinosaurier. Morphol. Jahrb., 

 Bd. 10, 1885, pp. 613-616. 



2 Baur, G. Zool. Anz., No. 216, 1886. 



' Baur, G. Uber die Kanaele im Humerus der Amnioten. Morph. Jahrb., Bd. xil., 

 1886, pp. 299-305. 



