MARSH.] 



TOROSAURUS. 



215 



nasal horn core is compressed, with a sharp apex directed forward. 

 The frontal horn cores are large and strongly inclined to the front, 

 extending apparently in advance of the nasal protuberance. The long, 

 slender squamosals diverge rapidly as they extend backward, their 

 outer margins being nearly on a line with the facial borders in the 

 maxillary region. 



The parietal forms more than half of the upper surface of the skull, 

 and' is the most characteristic element in its structure. In the poste- 

 rior part are two very large apertures, oval in outline, with their outer 

 margin at one point formed by the squamosal. The rest of the border 

 is thin and somewhat irregular, showing that the openings are true 



Fig. 54. — STjbII of Torosaurits gladius Marsh ; seen from above. One-twentieth natural size. 

 c. snpratempnral fossa; e', epijugal bone; /', parietal fontanelle; h t horn core; k', nasal horn core ; 

 p, parietal; 8, squamosal; z, pineal foramen (?) . 



fontanelles. This is still better seen in the second species represented 

 in the same plate, fig. 2, and in fig. 54, above. In the latter specimen, 

 however, these vacuities are entirely in the parietal, a thin strip of bone 

 separating them on either side from the squamosal. A second pair of 

 openings, much smaller, apparently the true supratemporal fossce, are 

 shown in the type specimen. These are situated mainly between the 

 parietal and squamosal, directly behind the bases of the large horn cores 

 (PI. LXII, fig. 1, c). The same apertures are represented in the genus 

 Triceratops by oblique openings, as in the skull shown on PL LX, fig. 

 3, c, where the front border of each is formed by the postfrontal. 



Between these openings, in the type of Torosaurus, is a third pair of 

 apertures (PI. LXII, fig. 1, &). These are quite small, nearly circular in 

 outline, and entirely in the parietal, although probably connected 



