380 Annals of the Carnegie Museum. 



"The remaining specimens of teeth referred with the former to 

 Trachodo)), are represented in Figs. 7-20 of the plate cited. Most of 

 them are so worn and probably altered from their original form, that 

 it is rendered uncertain whether they belong to the same animal as the 

 preceding tooth, and one unworn (Figs. 18-20) has a very different 

 shape from this. Perhaps these specimens belonged to another 

 Dinosaur, for which the name Trachodon might be reserved, while 

 that of Hadrosaitnis might include the first mentioned and more char- 

 acteristic tooth. 



"As Iguaiiodon had its enemy in a species oi Alcgalosaurus, Trach- 

 odon, the representative of the former both in the western and eastern 

 portions of the North American continent was accompanied by an 

 equally bloodthirsty enemy, which may, perhaps, on nearer compari- 

 son of corresponding parts, prove to be another species of the same 

 genus, until now supposed to be different, under the names of Dinodon 

 and Laelaps." 



From the above quotation it will be seen that Leidy now recognized 

 the distinct nature of the tooth shown in Figs. 18-20 of the plate 

 cited and at the same time considered Hadrosaiinis a synonym of 

 Trachodon. I fail however to see how he can be interpreted as hav- 

 ing abandoned the genus Trachodon, as Cope later seems to have con- 

 strued his words.* 



If Leidy was correct in considering Trachodon and Hadrosaiirus as 

 synonyms, the presence of remains of so highly a specialized genus of 

 the dinosauria in the fresh water Laramie deposits of the West and in 

 the marine upper green sands of the New Jersey Cretaceous would 

 seem to be of considerable importance in reaching a conclusion as to 

 the proper correlation of the Cretaceous deposits of these widely sep- 

 erated regions. 



Two new species, Trachodon (^Hadrosaurns) minor and T. {JTadro- 

 saiiriis) tripos, were proposed respectively by Marsh and Cope in 1870, 

 and described in the Proceedings and Transactions of the American 

 Philosophical Society. In 1871 Cope adds another species, T (^Had- 

 rosaieri/s) cavatiis, describing it in the Proceedings of the American 

 Philosophical Society for 187 1. The first of these three species was 



^See footnote, p. 99, Proc. Phil. Acad. Sci., 1883 and 1876, p. 253. In a later 

 communication (Proc. Phil. Acad. Sci., 1870, p. 68) than that cited by Cope Leidy 

 places Trachodon mirabilis as a synonym of Hadrosatirzis mirabilis, apparently over- 

 looking the fact that Trachodon has priority. 



