170 THE CERATOPSIA. 



The general form of the skull is long and low, the frill, which is twice as broad as long, 

 being but little elevated behind, in contrast to most of the other species except flabellatus. 



The median ridge of the parietal region is elevated and bears four rugose prominences, 

 wherein T. serratus differs from flabellatus and elatus, but agrees with prorsus and Irevicornus. 



The number of epoccipitals is seventeen, five pairs being borne on the squamosals. In 

 this, as in other features, the type specimen agrees with No. 970 of the American Museum, a 

 much larger though still immature skull which the present writer™ has referred to the same 

 species. 



5. Triceratops (Bison, Ceratops) alticornis Marsh (pp. 115-116, fig. 106) is known only from a 

 pair of remarkable supraorbital horn cores (No. 1871e, U. S. National Museum), first referred 

 by Marsh to Bison and later to Ceratops. Hatcher has removed the species to the present 

 genus for reasons which are at once evident when one contrasts the generic characters of 

 Ceratops and Triceratops, especially with reference to the relative development of the elements 

 represented by the type. 



The supraorbital horn cores are long, with slender-pointed ends, curving forward and 

 outward, then upward. 



These horn cores resemble possibly those of serratus more than any other species and rep- 

 resent the most highly specialized type within the genus. The frontal region is broad, somewhat 

 convex, and very rugose. 



6. Triceratops sulcatus Marsh (pp. 133-134, figs. 112, 113, PI. XXXVII) is based upon some 

 skull and skeletal fragments (No. 4276, U. S. National Museum) of a very large, fully adult 

 animal. 



In the original description Marsh describes a deep groove on the posterior surface of the 

 upper half of the supraorbital horn core. Unfortunately but one horn core is now available, 

 and it is incomplete, evidently having been broken off and healed over during the life of the 

 individual. This core does not show the distinctive groove, and Hatcher is inclined to give 

 the presence or absence of the groove but little specific weight. 



The horn was ovate in cross section and as preserved shows no distinctive characters. 

 This is also true of the humerus and vertebrae which are preserved. 



On the whole there seem to be no characters in the fragmentary material representing the 

 type which afford a basis for a true specific diagnosis. It would be well, therefore, to await 

 the discovery of additional material before deciding as to the validity of this species. 



7. Triceratops elatus Marsh (pp. 134-138, PI. XLIII) is based upon a scarcely adult specimen 

 of large size (No. 1201, U. S. National Museum). The rostral bone is of moderate size and is 

 not coossified with the premaxillaries, the upper branch being free. 



The nasal horn core is short and stout, its posterior border not being continuous with the 

 upper surface of the nasals as in most species. The apex rises but little above the superior 

 border of the nasals. Another skull (No. 4805, U. S. National Museum) has a horn intermediate 

 between that of the type and that of T. calicornis, evidently the nearest ally to the species 

 under discussion. 



The supraorbital horn cores are long and massive, curving strongly forward as in T. cali- 

 cornis, much compressed laterally except toward the apex, where they become nearly circular. 



The orbit is large, elliptical, with a somewhat oblique axis. 



The inferior process of the jugal is directed downward and backward at an angle of 45°, in 

 contrast to other species, wherein it is more nearly vertical. 



The frill is much elevated toward its posterior margin and differs from that of other species 

 in the absence of undulations along the margin of the squamosal, this bone being rather sharp 

 edged and regular in outline. Epoccipitals were borne on the parietals and the posterior half 

 of the squamosals only. The number of epoccipitals was fourteen, four pairs on the squamosals 

 and six on the parietals, without the usual median one. 



a Bull. Am. Mus. Nat. Hist., vol. 19, pp. 6S5-C95, PI. LIX. 



