CEEATOPSIAN DINOSAURS FROM MONTANA GILMORE 17 



with the squamosal, but the damaged condition of this border renders 

 its precise outline somewhat uncertain. The jugal thus forms the 

 external surface of the skull between the orbit and forward of the 

 infratemporal fossa. Its relations to the surrounding elements is 

 well shown in figure 11. 



If an epijugal was present in Bi^achyceratops it was extremely small. 

 A small rounded pit on the outer postero ventral border may repre- 

 sent the seat of this missing element (fig. 11). 



The lachrymal is a subquadrangular bone that fills the interspace 

 between the jugal below and the prefrontal (frontal of authors) and 

 supraorbital above. Its thickened posterior end contributes to the 

 formation of the anterior border of the orbit for a space of 42 mm. 

 Its lower anterior end is notched and forms the posterior boundary 

 of the preorbital fossa. The upper portion of this end was broadly 

 in contact with the nasal and probably the posterior branch of the 

 premaxillary, a point that cannot be positively determined from this 

 incomplete specimen. Viewed laterally the jugal-lachrymal suture 

 loops downward into the jugal as in Monoclonius^ instead of continu- 

 ing straight forward and downward from the orbit as in many 

 ceratopsians. 



The supraorbital is a rectangular blocklike bone whose thickened 

 outer border forms the upper anterior portion of the orbital rim 

 between the lachrymal below and the postorbital above. Internally 

 it is wholly in contact with the prefrontal. It is quite evident from 

 this specimen that there is early coalescence of the sutures and that 

 in aged individuals all trace of them would probably be obliterated 

 through fusion. This element was entirely missing in the type, but 

 its presence was indicated by the surrounding sutural borders. 



In the right maxillary the unworn crowns of seven young teeth are 

 preserved. Four are near the front of the dental series, probably the 

 second, third, fourth, and fifth. The other three are near the back 

 of the series. These teeth agree in all particulars with the young 

 teeth of the type specimen, which have been described.^® About the 

 only new information regarding the teeth to be gained from the 

 present specimen is that the anterior teeth are considerably smaller 

 than the posterior ones. The total number of teeth in the maxillary 

 series cannot be positively determined in this specimen, owing to 

 injury of the alveolar borders, but it would seem to be in accord with 

 the original determination of 20. 



A median portion of the right half of the nasal horn shows it to 

 be divided into right and left halves as in the type specimen. The 

 internal side is flattened, this surface being sculptured by alternating 

 longitudinal grooves and flat-topped ridges that probably fitted into 



"Gilraore, C. W., U. S. Geol. Surv. Prof. Paper 103, p. 16, figs. 18-20, 1917. 



