136 The Ottawa Naturalist. [February 



material above mentioned, to Hadrosaurus was recognized 4 by Leidy, 

 who also suspected that the ceratopsian tooth which he had included 

 in the description of Trachodon mirabilis might not properly belong 

 there 5 . He suggested that the best preserved tooth originally 

 referred to Trachodon might be included with Hadrosaurus, reserv- 

 ing for the ceratopsian tooth the generic term Trachodon. If this 

 suggestion were acted on Trachodon would necessarily become a 

 genus of horned-dinosaur. The term Trachodon, however, has passed 

 extensively into the literature of the North American dinosaurs in 

 connection with bipedal, herbivorous Cretaceous forms and, if retain- 

 ed as a name denoting a genus, had best remain with this association. 

 Unfortunately it has been used for the reception of inadequately 

 represented and imperfectly understood diverse forms of these dino- 

 saurs. from different horizons of the Cretaceous. 



The tooth of Trachodon, first mentioned in Leidy's original 

 description, and later figured first in his plate of illustrations and 

 referred to as being the most important of the specimens should be 

 considered the type of the genus. On the characters of this tooth, 

 therefore, must the validity of the genus Trachodon rest. The 

 tooth is from the lower jaw, and if the figure illustrating it be cor- 

 rect, and there is every reason for believing it so, it is very pointed 

 above. As regards the lithographic illustrations of Dr. Leidy's paper 

 of 1860 in the Transactions of the American Philosophical Society, 

 vol. XV., their artistic merit is so pronounced, and all the figures 

 of the three large plates have so much the appearance of being accur- 

 ate portrayals of the fossils themselves that it appears reasonable to 

 assume that the type tooth of T. mirabilis is not shown too pointed 

 at the apex. 



Since the days of this pioneer work many new forms of hadro- 

 saur dinosaurs have been described from excellent and wonderfully 

 complete material collected in the Cretaceous of the west both in 

 Canada and the United States, particularly in recent years from the 

 Belly River and Edmonton formations of Alberta. In none of the 

 Belly River genera best known from unusually perfect skulls, such 

 as Stephanosaurus Lambe, Gryposaurus Lambe, and Prosaurolophus 

 Brown, are the teeth acutely pointed as in Trachodon Leidy. It is 

 necessary, therefore, to conclude that the genus Trachodon is as yet 

 unknown in the Belly River, and fully or partially synchronous for- 

 mations, except from this single mandibular tooth. Nor is this genus 

 recognizable in the Edmonton and Lance formations, or their equiva- 

 lents, of the later Cretaceous, in such forms, known from nearly per- 

 fect skulls, as Diclonius Cope, "Claosaurus" Marsh, Saurolophus 



4 Smith. Contr. Know. vol. XIV, p. 84. 1865. 



5 Remarks on a jaw fragment of Megalosaurus, by Joseph Leidy, M.D., 

 Proc. Acad. Nat. Sci. Phila., vol. XX, p. 199, 1868. 



