TRICERATOPS CALICORNIS. 139 



horn, which, as will appear from a reference to Marsh's original description quoted above, 

 furnished the chief specific distinction. The jugal differs from that in the type of T. elatus in 

 that it falls directly below the orbit instead of being directed strongly backward as in the last- 

 mentioned species. It is more than probable, however, that this is due to the different manner 

 in which the two have been affected by pressure. 



In the type of the present species the skull is large, with elongate supraorbital horn cores 

 curved strongly forward. The orbits are large and elliptical, with the longer diameter inclined 

 slightly backward from the vertical. The nasal horn core is low and rises almost directly upward. 

 It is pointed above, convex in front, and concave behind, where it is overlapped by an anterior 

 prolongation of the nasals, with a convex and rugose superior surface which may be considered 

 as having formed part of the nasal horn core. The nasal horn core proper is supported in part 

 by the nasals and in part by the premaxillaries, but is an ossification distinct from either. 



The premaxillaries are very long and deep, but do not differ materially in form from those 

 of other members of the group. The rostral shows no peculiar characters, but the sutures 

 between it and the premaxillaries are open, indicating that the animal was young. The squa- 

 mosal is broad and elongate. At present only a small portion of the parietal is intact, though 

 more than half of it was originally preserved. The epoccipitals were not coossified with the 

 squamosals and parietals. The principal characters are well shown in Pis. XXXVIII and 

 XXXIX. 



The lower jaw. — When discovered the lower jaw was complete and in an excellent state 

 of preservation. Among the material in the National Museum I have been able to discover 

 only the predentary, with the anterior extremity of the left dentary. The latter shows a 

 freshly fractured surface, and it is more than probable that the remainder of this element at 

 least is buried somewhere among the Museum collections. 



The vertebral column. — The dorsal series is complete save for the eighth, ninth, and tenth 

 dorsals, which are wanting. The only marked character in the dorsals in the present species 

 is to be seen in the three posterior dorsals, where the neural spines are much broader and thinner 

 than in the same vertebrae in T. prorsus or T. brevicornus. The centra of tho anterior dorsals are 

 short and nearly circular in outline, while farther back in the series the centra become longer 

 and the vertical diameter considerably exceeds the transverse. (See PI. XL, figs. 2 and 3.) 



There are preserved portions of the cervicals and caudals, but they are not accessible. 

 The greater portion of the sacrum is present also, but this has not yet been prepared for study. 



The pelvis. — An ilium and pubis are nearly complete, but in the present state of preparation 

 show no special characters, save that the postpubis is rather better developed than in other 

 species. 



Principal measurements of type. 



Mm. 



Distance from anterior end of rostra] to posterior end of squamosal _ 2, 180 



Distance from anterior end of rostral to anterior border of orbit 1 , 010 



Distance from anterior end of nasal horn core to anterior border of orbit 635 



Distance from anterior end of rostral to postfrontal foramen 1 , 375 



Distance from inferior border of orbit to lower end of jugal 430 



Distance from superior border of orbit to apex of supraorbital horn core • 780 



Distance between orbits 440 



Longest diameter of orbit 185 



Shortest diameter of orbit 125 



Distance from posterior border of orbit to posterior surface of supraorbital horn core 262 



Circumference of supraorbital horn core at base - 960 



Circumference of supraorbital horn core 300 mm. above orbit - 450 



Antero-posterior diameter of supraorbital horn core at base - 370 



Transverse diameter of supraorbital horn core at base 175 



Transverse diameter of nasal horn core at base - - - 1 10 



Altitude of nasal horn core - - - 1 10 



Distance from posterior border of nasal opening to extremity of beak 605 



