Article XXX. — SKULL OF TRICERATOPS SERRATUS. 



By Richard Swann Lull, Ph.D. 



Plate LIX. 



The American Museum Expedition of 1902, under Mr. Bai- 

 num Brown and the writer, which was sent by Professor 

 Osbom into the Laramie formation of Montana had the good 

 fortune to secure, among other material, a fine specimen of 

 Tnceratops serratus Marsh. The exact locality in which the 

 specimen was found was in the wall of Hell Creek Canon, 

 some twenty-five miles from the Missouri River, and one 

 hundred and thirty-five miles noi^thwest of Miles City, 

 Montana. The unconsolidated sand matrix has been entirely 

 removed from the skull, thus affording an exceptional oppor- 

 tunity for the study especially of the remarkably preserved 

 palate. 



Through the courtesy of Professor Charles E. Beecher the 

 writer was permitted to study the type skulls of Tnceratops 

 prorsus and of T. serratus which are preserved in the Peabody 

 Museum at Yale University. This confirmed the opinion 

 already formed that the American Museum specimen is refer- 

 able to the latter species. The agreement between the speci- 

 mens is close, the main points of difference being the inferior 

 size of the type specimen, which is evidently that of a younger 

 animal, and that the median ridge of the parietal crest or frill 

 is not so prominent in the American Museum specimen; nor 

 are the bony projections along the ridge quite so conspicuous as 

 in the type ; but in general proportions, the form and arch of 

 the frill, the shape of the orbit and other points mentioned by 

 Marsh in his specific definition the resemblance is very close. 



Triceratops serratus Marsh. 



Marsh, O. C, 1890, Amer. Jour. Sci. (3) XXXIX, p. 81. 



Marsh, O. C, 1890, Amer. Jour. Sci. (3) XXXIX, p. 425.pl- v. fig. 2; 



pi. vi, figs. 1-6. 

 Marsh, O. C, 1896, Sixteenth Annual Report U. S. Geol. Survey, p. 



208; pi. Ix, fig. 3; pi. Ixi, figs. 7, 9, 10. 



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