420 Lull — Restoration of the Homed Dinosaur Dieeratops. 



Art. XLII — Restoration of the Homed Dinosaur Dieera- 

 tops ; by Richard S. Lull. (With Plate XIY.) 



The new genus and species described by Hatcher in the pre- 

 ceding article^represents perhaps the most bizarre and grotesque 

 form among all the race of horned dinosaurs, and the author 

 has attempted an interpretation for the purpose of empha- 

 sizing the features wherein this animal differed from any of 

 its allies. 



Dieeratops comes from the Laramie of Converse County, Wyo- 

 ming, and while contemporaneous with Triceratops and Toro- 

 saurus it is probably as late in geological time as any of the 

 species of either genus, and may be said to represent the cul- 

 mination of at least one phylum of the Ceratopsia. Dieeratops 

 differs from Torosaurus in the proportions of the skull, for in 

 the latter genus the frill is relatively huge as contrasted with 

 the abbreviated facial region. In this Dieeratops and Tricera- 

 tops agree, and it is quite evident that there is a genetic rela- 

 tionship between these genera, while Torosaurus represents a 

 totally distinct phylum. 



Perhaps the most notable point of distinction between Tri- 

 ceratops and Dieeratops is the presence of a fairly well deveh 

 oped nasal horn in the former while in the latter genus it is 

 lacking, a feature which in the author's mind represents the 

 culmination of specialization. 



The earliest known Ceratopsia are the Judith .River types, 

 characterized by an incomplete frill, by rudimentary horns 

 above the eyes, and by a very well developed, generally erect 

 or backwardly curved nasal horn. 



The supraorbital horns are progressive structures while the 

 nasal horn is retrogressive, and during the lapse of time between 

 the Judith River and Laramie periods, when the marine Bear- 

 paw shales and Fox Hills sandstones were laid down, the Cera- 

 topsia underwent a remarkable though unrecorded evolution, 

 for when they again come into view in the Laramie the arma- 

 ment is reversed, in that the great temporal horns are by far 

 the larger and more efficient weapons, and the diminishing 

 nasal horn, while supplementing the others in the various spe- 

 cies of Triceratops and Torosaurus, is vestigial in the form 

 under discussion. 



This change of armament was necessarily accompanied by 

 a change in the method of attack, for while the Judith River 

 types probably used the one horn much as the rhinoceros does, 

 with an upward thrust, Triceratops seems to have charged with 

 lowered head, the small forwardly directed nasal and the larger 



