378 Annals of the Carnegie Museum. 



pertain to a distinct genus. Moreover this would seem to be the 

 view taken by the late Professor Marsh when in 1890 he described as 

 Trachodon longiceps the lower jaw of an Iguanodont dinosaur with 

 very similar, if not identical, simple-rooted teeth. ^ The type of T. 

 longiceps was obtained by the present writer in about the same hori- 

 zon, though in a different locality, as were the teeth described by 

 Dr. Leidy. 



In December, 1856, under the name of Thespesius occidentalis Dr. 

 Leidy described two caudal vertebrce and a first phalanx of a large 

 dinosaur.* These remains were found in the lowest member of the 

 Lignite formation, essentially the same horizon as those from which 

 the teeth were procured. 



Two years later or in December, 1858,^ Dr. Leidy described a third 

 new genus and species of Iguanodont dinosaur under the name of 

 Hadrosaiinis foulkii. The remains upon which this genus and species 

 were founded were taken from the Cretaceous marls near Haddonfield, 

 New Jersey, and consisted of twenty-eight vertebrje with their proc- 

 esses mostly wanting ; a complete humerus, radius and ulna ; an 

 imperfect ilium and pubis ; a femur, tibia and fibula ; two metatarsal 

 bones and a first phalanx, nine teeth and a fragment of the lower jaw. 

 These remains were later more fully described and adequately illus- 

 trated by Dr. Leidy. "^ In this paper Dr. Leidy fully realized the very 

 close relationship and probable identity of the genera Trachodcvi, 

 Thespesius and Hadrosaiinis which he had proposed for the reception 

 of these remains from three widely separated localities. On page 84 

 he says "several of the teeth of Hadrosaiinis are nearly identical in 

 form and details of structure with the specimen of a tooth discovered 

 a short time previously to the former, by Dr. F. V. Hayden, in the 

 Bad Lands of the Judith River. The tooth just mentioned, together 

 with several other much worn specimens, I referred to a distinct genus 

 under the name of Trachodon, but I shall not be surprised to learn 

 that future discovery determined Hadrosaiinis and Trachodon to be 

 the same." While in a footnote on the same page in speaking of 

 Thespesius he says, "had the remains of Thespesius and Trachodon 

 been found in a deposit of the same age I should have unhesitatingly 



3 See Am. Jour Sci., 1890, Vol. XXXIX., p. 422. 

 ♦See Proc. Acad. Nat. Sci. of Phil., 1856, p. 311, 312. 

 5 See Proc. Acad. Nat. Sci. of Phil., 1858, pp. 215-218. 



•"See Cretaceous Reptiles of the United States. Smith. Contr. to Knowledge, 

 Ig65, Vol. XIV., pp. 76-97, Plates XII. -XVII. 



