XI\'. THE (IHNKkA AND Sl'KCIES OF THE TRACHO- 

 DOXrin.E (HADR0SAURH3.^, CLAOSAURID.-E) Marsh. 



Bv J. ]]. Hatcher. 



In March 1856 ' Dr. Joseph Leidy described under the name of 

 Tracluhlon mirabilis certain teeth pertaining to a herbivorus reptile 

 allied to Iguanodon. These teeth were discovered by Dr. F. \ . Hay- 

 den in deposits, now generally considered as l>aramie, in the "Bad 

 Lands" of the Judith river, in Montana. No figures accompanied 

 Leidy's original descrii)tion. Three years latter however Dr. Leidy 

 gives a more detailed description of this new genus and species accom- 

 panied by excellent figures of the teeth upon which it was founded.^ 

 L-nfortunately Dr. Leidy failed to designate any particular tooth as 

 the tyi)e of the genus and species and his figures show that he has in- 

 cluded teeth belonging to two quite distinct forms of dinosaurs. 

 Figs. 1-17 represent teeth with simple roots closely resembling 

 the teeth of certain Iguanodont dinosaurs, which by Leidy, Cope, 

 Marsh, and others have since been variously referred to under the 

 names of Trachodon, Thespesius^ Hailrosaiims, Diclonius, C/aosaurus, 

 etc. Figs. 18 to 20 represent different views of a tooth with two 

 roots and of quite a different pattern. This tooth, as we know by 

 later discoveries, belonged to a very different dinosaur pertaining to a 

 family, representatives of which have since been described by Cope 

 and Marsh under various generic names as Dyss^a/ii/s, Agathaiinias, 

 Monoclouius, Cera/ops, Triceratops, Tofosauri/s, etc. 



While Leidy has nowhere designated any of the teeth described and 

 figured in the above mentioned publications as the type of Trachodon 

 mirabilis, yet on page 141 of the paper last cited he says : " Of the 

 specimens of teeth referred to Trachodon, the unworn crown is the 

 most important. It is represented in plate 9, figs. 1-3." This may 

 then be very properly considered as the type of the genus and species, 

 while the quite different two-rooted tooth above referred to would 



•See Proc. Phil. Acad. Sci., 1S56, p. 72. 



'^See Trans. Am. Phil. Soc, 2d Ser., Vol. II . pp. 140-143. I'l- 9. f'gs- »-'''• 



877 



