NO. 22G0. NEW RESTORATION OF TRICERATOPS-GILMORE. 101 



great variation, as might well be expected in such highly specialized 

 outgrowths, and the differences in sex, and stage of growth present 

 other features that have also to be considered before a satisfactory 

 conclusion can be reached as to what characters constitute valid spe- 

 cific differences. In fact, the whole group needs restudying. Such 

 a revision assisted by the considerable number of new specimens 

 discovered since the writing of the Ceratopsia monograph in 1907 

 may enable an investigator to straighten out this confusion. At the 

 present time it appears quite certain that the number of described 

 species is too great by a considerable number. 



THE TYPE-SPECIMEN OF TRICERATOPS CALICORNIS MARSH. 



At the time of writing the Monograph on the Ceratopsia, Hatcher^ 

 and Lull mentioned their inability to locate in the collections of the 

 United States National Museum the lower jaws pertaining to the 

 type-specimen of THceratops caliconiis Marsh, No. 4928, U. S. 

 N. M. Upon opening a large box, listed as containing the 

 skull of another individual in it was found the long misplaced 

 dentaries. These are in an excellent state of preservation. In the 

 same block of sandstone with the lower jaws was a posterior cervical 

 vertebra and portions of several thoracic ribs. 



The vertebra is from the posterior part of the neck and represents 

 the seventh of the series counting backward from the skull, or it 

 belongs behind the first of the series as illustrated in figure 2, plate 

 40, of the monograph cited above. Figure 2, Plate 5, shows this 

 vertebra inserted in its proper position in the vertebral series. That 

 this is the correct position of this element in the vertebral column is 

 clearly shown by the shape and length of the transverse processes 

 and also by the perfect articulation of the zygapophyses. 



The dentaries except for their great size are similar to those of 

 other described species, and the few minor differences observed do not 

 add anything to the diagnosis of the species. 



The principal measurements of the dentaries are: 



mm. 

 Greatest lengtli 045 



Greatest depth 170 



Length of dental series 480 



In the left ramus there are 38 rows of teeth in the dental maga- 

 zine. 



The type-specimen now completely assembled consists of the fol- 

 lowing parts : 



Skull, lacking some parts of the frill, lower jaws, 2 cervical verte- 

 brae (portions of atlas and other cervicals), 10 dorsal vertebrae (por- 

 tions of other dorsals), 5 cervical ribs, 2 thoracic ribs (many parts 



1 Monograoh 4".). U. S. Geological Survey, 1907, p. 139. 



