TRICERATOPS PRORSUS. 



129 



nearly circular orbit; (4) the position of the infraorbital foramen below the superior border 

 of the ascending branch of the maxillary, as in Sterrholophus flabellatus. 



Viewed from the side, the facial region of the skull of the present species appears long and 

 the parietal crest proportionally abbreviated, presenting the opposite conditions from those 

 which obtain in the genus Torosaurus, where the parietal crest is greatly elongated and the 

 frontal region much abbreviated. The superior surface of the region between the supraorbital 

 horn cores and the posterior border of the frill is strongly concave, though this condition has 

 doubtless been somewhat accentuated by crushing. A rather sharp and elevated ridge marks 

 the middle lines, displaying a series of three small rugose elevations. The jugal is directed 

 downward and slightly backward and is firmly coossified with the epijugal. The union between 

 these elements and the quadratojugal is less complete, though these are coossified below, while 

 the suture between the jugal and quadratojugal is left open above throughout fully two-thirds 

 of its length. The quadratojugal notch is deep and narrow, more so than in any other skull 

 known to the writer. The squamosal is proportionally broad and short and bears seven 

 epoccipitals. The smallest of these is at the antero-inferior angle, which is rather less promi- 

 nent than in most other species of the family. The posterior border of the frill is incomplete 

 and it is therefore impossible to determine with accuracy the number of epoccipitals borne by 



Fig. 109.— Anterior part of skull of type of Triceratops prorsus Marsh (No. 1822, Yale Museum). 1, Side view; 2, front view; 3, inferior view. 

 h', Nasal horn core; to, nasal bone; na, narial aperture; pm, premaxillary; r, rostral. One-eighth natural size. After Marsh. 



the parietals, though the number seems to have been five, one median and four lateral, 

 arranged two on either side, making nineteen in all, as figured by Marsh and shown here in 

 Pis. XXXII and XXXIV. There is no postfrontal (pineal) foramen. ° 



Owing to the advanced age of the individual, it is impossible to determine to just what 

 extent the various cranial elements enter into the construction of the orbital borders. The 

 powerful supraorbital horn cores are directed forward and upward at an angle of about 45° 

 from the perpendicular. The long and pointed nasal horn is directed nearly straight forward 

 and only very slightly upward. The superior surface of the nasals and nasal horn core are in 

 nearly the same plane. The nasal horn reaches as far forward as the short and compressed 

 rostral, which embraces the premaxillaries anteriorly and is completely fused with them. The 

 rostral is deeply excavated beneath and presents on either side a sharp, cutting edge. It is 

 very rugose and was doubtless in life incased in a heavy sheath of horn or other substance 

 resembling, on a large scale, the beak of modern birds and turtles. With a similar beak borne 

 by the predentary of the lower jaw, which fitted into and opposed from beneath that borne on 

 the rostral, these elements afforded the most effective means for procuring the food necessary 

 for the sustenance of the individual and at the same time must have served as very efficient 



"See note on p. 24.— R. S. L. 



MON XLIX — 07- 



