19 



generic ^ types of these animals Traclwdon viirabilis, Leidy (1856) is Judith River ; Thespe; 

 sius occidentalis, Leidy (1856) is from " essentially the same horizon " (Hatcher) in Montaua- 

 Claosaurus agilis, Marsh (1872) is from the Mid-Cretaceous, Pteranodon heds (Colorado 

 series, probably more nearly equivalent to Belly Itiver) ; Cionodon, Cope (1874), Colorado ; 

 Diclonius, Cope (lJ?76) ; Pteropelyx, Cope (1889) from Cov\'' island, 40 miles below the 

 mouth of the Judith river, (Hatcher) Montana; finally Claorhynchus, Cope (1892) 

 regarded by this author as one of the Agatliaumidcr, by Hatcher (op. cit., p. 382) as an 

 iguanodont. 



•■ii 



Of undoubted Upper Cretaceous age is Hadrosaurus foulkii, Leidy (New Jersey). 



The separation of Mid- from Upper Cretaceous iguanodonts will, if confirmed by 

 closer examination and determination of geological horizons and levels, greatly increase 

 our understanding of this most interesting group. Without professing to have made an 

 adequate investigation, the writer is strongly of the opinion that the Cretaceous includes 

 a number of distinct genera, representing a wide adaptive radiation and probably a 

 number of successively parallel phyla. The wide differences in the mode of succession, 

 general shape and border sculpturing of the teeth, indicate profound changes which 

 required an enormous period of time for their development. 



In the Belly River series we find the new species Trachodon selwyni, Lambe, an 

 animal nearly double the size of the Iguanodon manteUi of the English Wealden (Upper 

 Jurassic). A more delicately built iguanodont, P. marginatus, Lambe, resembles the less 

 robust iguanodont Pteropelyx grallipes, Cope, but is specifically distinct in the border 

 sculpture of the teeth. A third new species, or even genus P. [Didanodon) altidens, 

 Lambe, distinguished by exceptionally high narrow teeth. 



There are therefore indications of a separation of the Iguanodonts into light and 

 heavy limbed series, smaller and larger, swifter and clumsier, of great variety in tooth 

 structure. 



DiNOSAURiA : Ceratopsia. In this order, perhaps more than in any other, the resem- 

 blance between the Belly River and Montana stages and the contrast between these and 

 the Wyoming Laramie stages, so far as known, are distinctly marked. 



* Mr. J. B. Hatcher has just published (.^nnals of the Carnegie Museum, 1902. Vol. I, Art. XIV. p. 377) a syste- 

 matic review of these animals : " The Genera and Species of the Tracliodontidie (Hadrosauridte, Claosaurida;), Marsh.'' 

 He reaches the conclusion : " A careful examination of the original descriptions and figures of the types of the ten 

 genera and twenty species enumerated above, shows that there should be a great reduction in each and that the ten 

 genera which have been proposed should be reduced to two Trachodon, Leidy, and Claosaurus, Marsh, while the remaining 

 Height genera should be treated as synonyms of Trachodon, which should also be made to include T. (Claosaurm) avue- 

 / enii, Marsh ; while the smaller Claosaurus agilii described by Marsh from the Kansas chalks may still be considered as 



pertaining to a distinct genua Doubtless many of the species are also synonyms but this can only be 



determined by a careful comparison of the types. " 



