TRICF.RATOPS MAXIMUS 129 



Yet a third specimen in the National Museum, No. 1208, has been referred to this species. 

 This consists of a nasal horn and a pair of brow horns, only one of which shows the sulcations 

 which give the name to the species. Marsh's description states that "the most distinctive character 

 of the skull is seen in the horn cores of the frontal region, which are very large and elongate. On 

 the posterior surface of the upper half of each horn core, there is a deep groove, which has suggested 

 the specific name." 



The holotype, unfortunately, includes at present only a portion of one brow horn, which is 

 obliquely truncated distally as though broken during the lifetime of its owner, and this does not 

 show the distinctive sulcation on the rear, of which Marsh spoke. Possibly, as Hatcher suggests, 

 the mate to this horn, which cannot now be located, was the one which showed the distinctive 

 character. 



The plesiotype, No. 4286, shows the sulcations on both horns very well, but they are on the 

 antero-internal and not the posterior face of the horn. 



In the third specimen, No. 1208 U.S.N. M., 92 the left horn has a rather shallow sulcation on 

 the anterior side and a much deeper one on the antero-internal face, extending throughout the 

 distal two-thirds of the horn. The sulcations on the other horn are so slight that they might be 

 taken for vascular impressions were attention not called to them. 



Sulcated horns are rare and, other than those we have mentioned, the only additional recorded 

 instances are in the type of Arrhinoceratops brachyops from the Edmonton (see PI. XII), and a 

 slight indication of one on the antero-internal face of the left horn of Torosaurus latus type, 

 and of the right horn of Triceratops brevicornus type. I doubt, however, the specific value of this 

 feature alone, especially as there are no other diagnostic characters with which to correlate it. Both 

 No. 4286 and No. 1208 possess associated nasal horns, that of No. 4286 being small and pointed, 

 arising as a separate ossification which is now coossified with the underlying nasals. This horn does 

 not rise above the level of the nasal profile and the anterior face slants slightly forward. In 

 No. 1208, the dorsal outline of the nasals is slightly undulating, there being a low but distinct 

 hump over the nares, then a depression, in front of which is a very small, rounded nasal horn with 

 a nearly vertical anterior face, as preserved. Thus, the two nasal horns agree in being small; 

 otherwise, they are quite unlike. 



The lower jaw, associated with the holotype, is not specifically distinctive. 



At present, therefore, the species Triceratops sulcatus cannot be defined. Although it may ulti- 

 mately prove to be a distinct form, one cannot even determine its relationship with other Triceratops 

 phyla except by elimination. If either of the nasal horns is distinctive, sulcatus cannot belong to 

 the prorsus-brevicomus-horridus group; but whether its relationship lies with the obtusus or the 

 elatus phylum, the evidence does not show. 



Triceratops maximus Brown 93 



Holotype: No. 5040 A.M.N.H., a series of eight free vertebrae and two cervical ribs. 

 Horizon: Lance formation, Hell Creek beds. 



Locality: Rock Creek, 20 miles south of Lismas, Garfield County, Montana. 

 Collector: P. C. Kaisen, 1909. 



Specific characters, as given by Brown, are as follows: "Axis rib reduced in size. Third cervical 

 rib massive. Centra of free cervical vertebrae short, vertical and transverse diameters of articular 

 faces nearly equal; sides deeply constricted; ventral surface flat. Anterior dorsal centra higher than 

 broad." 



Brown stresses further the deeply excavated sides and the flat, very rugose, ventral surfaces of 

 the cervicals, the extremely large neural canal, a vertical series of three large foramina on each side 

 of the cervical centra, spaced approximately one inch apart, and the extraordinary size of all the 

 vertebrae. 



92 Hatcher, Marsh, Lull, 1907, PI. XXXVII. 



93 Brown, B., 1933, A. 



