1918] The Ottawa Naturalist. 137 



Brown, Cheneosaurus Lambe, and Edmontosaurus Lambe. In fact 

 a smooth margined normally shaped tooth as pointed as the type 

 of Trachodon is not found in any of the above mentioned genera of 

 Belly River and later Cretaceous times. If the name Trachodon is 

 to be retained it can only be regarded as denoting a genus based on 

 a tooth supplyng as yet insufficient diagnostic characters. If the 

 tooth is normal in shape the genus it represents is not recognizable 

 among the many forms now known from comprehensive and well 

 preserved material. If the tooth is abnormal it has little or no 

 value from a palapontological standpoint and the name Trachodon 

 had best be discontinued in use. 



As a result of the variety of hadrosaurs discovered of late 

 years, principally in the Cretaceous of Alberta, Canada, we now 

 have accurate knowledge of many genera displaying a wonderful vari- 

 ance in cranial development in crested and non-crested forms from 

 Stephanosaurus, with a skull higher than long, to Diclonius with a 

 lengthened and very depressed head. 



Hatcher in 1902'' in a paper on the genera and species of 

 Trachodontidae, expressed the opinion that two genera only, Tracho- 

 don Leidy and Claosaurus Marsh (represented by C. agilis), should 

 be retained of the many proposed prior to 1892. That many of the 

 genera and species referred to in his paper are founded on insufficient 

 material is obvious. The many discoveries of late years of crested 

 and non-crested types make it desirable that a thorough revision of 

 the family should be now undertaken. 



As regards the name of the family, for the reception of the 

 various genera of North American Cretaceous bipedal, herbivorous 

 dinosaurs, the term Hadrosauridae was proposed by Cope in 1869'. 

 (1871), and has precedence to Trachodontidae used by Lydekker in 

 1888 s , and later by Marsh in 18Q0'. Quite apart from any 

 question of precedence the name Hadrosauridae is much to be pre- 

 ferred of the two when we consider the material on which the genera 

 Trachodon and Hadrosaurus are founded. The characters of Tra- 

 chodon are unknown beyond those of the single mandibular tooth con- 

 stituting the type, although many have been assigned to it for whch 

 there is no warrant. The material on which Hadrosaurus rests in- 

 cludes a number of cervical, dorsal, and caudal vertebrae, the prin- 

 cipal bones of the fore and hind limbs, an ilium, an ischium, a 

 portion of a dentary bone, and a number of both upper and lower 

 teeth; unfortunately the cranium is not represented. 



"The genera and species of the Trachodontidae (Hadrosauridae, 

 Claosauridae) Marsh. Annals of the Carnegie Museum, vol. I, pp. 377-386. 



'The extinct Batrachia, Reptilia, and Aves of North America, Trans. 

 Am. Philos. Soc. vol. XIV, new series, 1871, p. 91. 



s Cat. of fossil Reptilia and Amphibia in Brit. Mus., pt. I, 1888, p. 241. 



'Additional characters of the Ceratopsidae. with notice of new 

 Cretaceous dinosaurs. Am. Journ. Sci., third series, vol. XXXIX, 1890, p. 424. 



