150 THE CEKATOPSIA. 



The present genus appears to be distinct from any of the others that have been proposed 

 for these larger members of the Ceratopsidae, either from this or other localities. The more 

 important differences are to be found in the parietal and squamosal regions of the skull. In 

 the present genus that portion of the skull posterior to the frontal horn cores is considerably 

 elongated, while the anterior portion is correspondingly abbreviated and more compressed 

 than in Triceratops. The most prominent and distinctive characters, however, are to be found 

 in the parietal crest, which is pierced by a pair of large foramina, situated one on either side 

 of the median line, as shown in fig. 12, and designated as the supratemporal fontanelles or 

 parietal foramina. The squamosals are also characteristic, being long and slender, assuming 

 somewhat the form and pattern of a broadsword, instead of short and broad, as in Triceratops 

 (see fig. 14; 1, 2, 3). As already remarked, the parietals in the present genus most nearly 

 resemble the same elements in the type of Monoclonius (M. crassus), and there seems little 

 doubt that the last-mentioned genus was ancestral to Torosaurus. a 



Torosaurus latus Marsh. 1891. 



The type (No. 1830, Yale Museum), from the Laramie of Converse County, Wyo. 



Original description in Am. Jour. Sci., 3d ser., vol. 42, September, 1891, p. 266. 

 Marsh, O. C, Am. Jour. Sci., 3d ser., vol. 43, p. 81; Sixteenth Ann. Rept, U. S. Geol. Survey, 1896, pt. 1, p. 214. 

 Lambe, L. M., Contr. Canadian Pal., vol. 3 (quarto), pt. 2, p. 66. 

 Osborn, H. F., ibid., p. 14. 



LOCALITY. , 



The type (No. 1830, Yale Museum) was discovered at the locality marked +19, PI. LI. 

 It lay embedded in an extremely hard bluish calcareous sandstone concretion near the summit 

 of the bluff on the north side of Lightning Creek, about 2 miles above the mouth of that stream, 

 in the bottom and near the extreme head of a small, dry watercourse emptying into Lightning 

 Creek. When discovered the summits of the frontal horn cores and most of the parietal crest 

 had already weathered out and been carried away by the current of water which at times filled 

 the channel of the. small watercourse, due either to occasional heavy rains or the melting of the 

 winter's accumulation of snow. Associated with the skull in the same concretion there were, 

 in considerable numbers, plant impressions and small lignitized stems. 



ORIGINAL DESCRIPTION. 



Professor Marsh's description of the type of the present species was as follows: 



Another well-marked species of this group, which may be referred to a new genus, is represented by one skull, and parts 

 of the skeleton, from nearly the same horizon as the specimen above described. One of the most striking features of the 

 present species is seen in the posterior crest, which, instead of being complete, as in the skulls hitherto found, is perforated by 

 a pair of large openings. These are in the parietals, but they have the inner margin of each squamosal for their outer border. 

 They are well behind the supratemporal fossa?, but doubtless were originally connected with them. They may be called the 

 supratemporal fontanelles. The squamosal bones, moreover, are very long and slender, and distally only show near the ends 

 sutures for union with the parietals. Another distinctive character is seen in the main horn cores, which are placed well back 

 of the orbit. The nasal horn core is short, with the apex compressed, and directed forward. 



This genus is of much interest, as it represents an earlier and less specialized form than either Ceratops or Triceratops, 



both of which have the posterior crest complete. The existing chameleons show the other extreme, where the outline only 



of the parietal crest has been attained. 



Some of the principal dimensions of this skull are as follows: 



Inches. 



Length from apex of nasal horn core to extremity of squamosal 80 



Distance from same apex to front of orbit _ 21 



Distance from same to front of parietal opening 54 



Width between posterior extremities of squamosals 56 



This important specimen was discovered by Mr. J. B. Hatcher in the Laramie of Wyoming. 



o This section of the manuscript is as origijialli/ written, not having been revised by the author, who later changed his views with regard 

 to the ancestry of the genus (see p. 100). — R. S. L. 



