OX CERTAIN GENERA AND SPECIES OF CARNIVOROUS 

 DINOSAURS. WITH SPECIAL REFERENCE TO CERA- 

 TOSAURUS NASICORNIS MARSH. 



By Oi.ivi'.i: P. Hay. 

 Of Washington, District of Columbia. 





Through the liberality of the officers of the United States National 

 Museum the writer has been enabled to prepare the following 

 paper, which is based mainly on specimens in the possession of the 

 Museum. Nearly all these specimens were originally collected by 

 Prof. O. C, Marsh while acting as Vertebrate Paleontologist of the 

 U. S. Geological Survey. 



1. THE GENUS LABROSAURUS MARSH AND ITS SPECIES. 



In 1870" Marsh established the genus Labrosaurus, with his Allo- 

 saurus lucaiis as the type. This species had been described in 1878 6 

 and was based on materials found in the Upper Jurassic of Colorado. 

 In this earliest description there was mentioned only an anterior 

 dorsal vertebra. In the description of 1879 cervical and dorsal 

 vertebra 1 and fore-limb bones were briefly described. So far as the 

 writer knows, no part representing this species has ever been figured. 



In 18S4 '' Marsh added a second species to the genus. Ldbrosaurus 

 ferox. The only part of this animal that was mentioned is the left 

 dentary. Marsh here made the statement that in Labrosaurus the 

 teeth are more triangular than in the other genera of the order; but 

 whether or not this statement had its basis in this specimen is 

 doubtful, inasmuch as the crowns of all the teeth are missing and 

 the roots almost wholly concealed by matrix. This dentary bone 

 (Cat. No. 2315. U.S. N.M.) probably came from the same locality 

 and level as the type of L. lucaris. 



In 1896 d Marsh again mentioned this >pecies and presented the 

 same figures. In a footnote on page 163 he remarked that the skull 



" Amer. Jour. Sci., XVIT, p. !>1. 



6 Idem., XV. p. 243. 



"Idem., xxvii. p. ::::::, pi. in. figs. t-6. 



d Dinosaurs of North America, pp. 1C>.">. 12TO, pi. xni. liu's. L! I. 



Proceedings U. S. National Museum, Vol. XXXV— No. 1 648. 



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