Maryland Geological Survey 207 



Family STEGOSAURIDAE 



Genus PRICONODON Marsh 



Priconodon orassus Marsh 



Plate XX, Figs. 5, 6 



Priconodon crassus Marsh, 1888, Amer. Jour. Sci., ser. iii, vol. xxxv, p. 93, 



figs. 7-9. 

 Priconodon crassus Marsh, 1896, 16th Ann. Rept. U. S. Geol. Survey, pt. i, 



pi. xllv, figs. 2a, b, c. 



Description. — The type specimen is a single tooth (No. 2135, TJ. S. 

 National Museum) from near Muirkirk. Marsh's original description 

 is as follows : " The existence of another herbivorous Dinosaur in the 

 same horizon of the Potomac formation is indicated by a number of 

 fragmentary remains, the most characteristic of which is the tooth fig- 

 ured below. This may be regarded as the type specimen. Although 

 resembling somewhat the teeth of Diracodon from the Jurassic of the 

 West, it is quite distinct. It has the narrow neck, swollen base, and 

 flattened crown of that genus, but the serrated edges meet above at a 

 sharp angle, instead of forming a wide curve at the apex. The surface 

 shown in fig. 7 is much worn by the opposing tooth. In fig. 9, the pit 

 formed by the succeeding tooth is seen near the top of the fang. The 

 other remains at present referred to this species were not found with this 

 tooth, and hence, their relations to it are uncertain. They will be de- 

 scribed more fully elsewhere." 



The prominences producing the serration of the edges of the crown 

 are continued down on either face of the crown in delicate; curved ridges 

 except where obliterated through wear. The swollen base is separated 

 from the blade-like crown, forming a prominent shoulder from which a 

 single ridge runs nearly straight upward toward the apex. There re- 

 mains but little of the fang of the tooth, but it appears to have been 

 nearly cylindrical, as in Btegosaurus and Diracodon. 



DIMENSIONS 



Width across crown 9.7 mm. 



Thickness 6.3 mm. 



Height of crown above shoulder 6.5 mm. 



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