TRICERATOPS ELATUS. 



137 



The specimen under consideration furnishes the first example of a free coronoid yet observed 

 in the Ceratopsia, although this element is doubtless present in all the other genera and species 

 of the group, usually, however, being so completely fused with the coronoid process of the den- 

 tary as to appear a portion of that element, more especially in old individuals. Its general 

 form and position relative to the surangular and the coronoid process of the dentary are well 

 shown in fig. 114. It is triangular in outline, terminating below in a sharp, spout-like process 

 which clasps about the posterior border of the base of the coronoid process. Its anterior 

 border is produced into a sharp edge, 

 which overlaps the inner surface of the 

 coronoid process; the superior and pos- 

 terior borders are thick and strong. 



As in other members of the Ceratop- 

 sia, the posterior border of the coronoid 

 process presents a deep vertical groove 

 for the reception of the anterior extrem- 

 ity of the surangular. The mandibular 

 fossa is deep, and at its anterior extrem- 

 ity a large foramen enters the dental 

 chamber. There appear to have been 

 four teeth in place in each vertical series, 

 so that the number of longitudinal series of teeth in the jaw would be eight. 



The surangular is not entirely complete. It is rather elongate, and is heavier than in 

 Triceratops prorsus. Near its anterior extremity it is pierced by a large external mandibular 

 foramen. On its inner side, just in advance of the projection in front of the articular, there is 

 the opening of a large foramen. A short distance beneath the surface this foramen branches; 

 one branch, the anterior, runs forward and opens on the external surface of the bone at a point 

 midway between the internal openings of this foramen and that of the anterior external mandib- 

 ular foramen mentioned above. The other or posterior branch of this foramen has its external 

 opening on the posterior border of the surangular near the external border. Near the inferior 

 border of the external surface of the bone there are two foramina opening near together, and it 

 is probable that these also connect with the large foramen already mentioned as opening on the 

 inner surface of the bone. 



As shown in fig. 115, the nasal horn core is of peculiar form, and was derived from a center 

 of ossification distinct from either the nasals or premaxillaries. It is short and stout, somewhat 



Fig. 114. — Internal view of right mandible (No. 4805, U. S. National Museum) 

 of Triceratops elatus, cotype [plesiotype]. C, Coronoid; sa, surangular; 

 mf, mandibular fossa; sy, symphysis. One-eighth natural size. 



Fig. 115. — Nasal horn core of Triceratops elatus, cotype [plesiotype], No. 4805, U. S. National Museum. A, Right side view; B, oblique 

 back view; C, posterior view; D, sutural surface for contact with nasals. One-fourth natural size. 



compressed laterally, and shows distinct sutural surfaces for contact with the nasals and pre- 

 maxillaries. Posteriorly on either side it sends downward and backward a thin blade of bone 

 which clasps over the anterior extremities of the nasals. The posterior surface of the nasal 

 horn core is rather smooth and slightly excavated, the anterior is convex, very rugose, and pre- 

 sents a number of deep vascular grooves, one of which runs continuously from the apex to the 

 base of the horn core. The character of this nasal horn core differs somewhat from that of the 

 type of the species, though at the same time presenting certain similarities not seen in the same 



