152 The Ottawa Naturalist. [Feb. 



The squamosal of Chasmosaurus is remarkable for its 

 length, although in comparison with the total length of the head 

 it is shorter than in Torosaurus gladiits, Marsh of the Laramie. 

 It is transversely concave throughout its length and from near 

 the squamoso-parietal suture slopes downward and outward 

 with a slight upward flare at the free border. Anteriorly, it 

 effects a long sutural junction with the postfrontal and is over- 

 lapped by the jugal. It encloses the lateral temporal fossa 

 behind and throws forward a process which forms the greater 

 part of the lower margin of this opening. Its front free border 

 is at right angles to the length of the bone and constitutes the 

 back border of a well defined quadrate notch. Its antero- 

 lateral angle is evenly rounded. Behind its union with the post- 

 frontal its superior surface is broadly rounded transversely and 

 descends rapidly backward to the general level of the parietal 

 portion of the frill. Behind the jugal its surface is almost 

 vertical. In its hinder half the broad front elevation is con- 

 tinued backward as a narrow ridge next to the squamoso- 

 parietal suture. Anteriorly within it overhangs the opening of 

 the supratemporal fossa. 



In lateral aspect the jugal is narrow in its lower portion, 

 and evenly rounded at the extremity. Above, it enters into the 

 formation of the lower margin of the orbital rim to some extent. 

 Laterally in front it overlaps the maxilla, and posteriorly above 

 it meets the postfrontal and sends out an extension which forms 

 the front and upper margin of the lateral temporal fossa and 

 overlaps the squamosal for some distance back of this opening. 

 Its ] osterior 1 order does not assist in enclosing the lateral 

 temy oral fossa 1 clow, 1 ut what appears to be a broken surface 

 on the 1 order beneath the level of the opening suggests a con- 

 vexity in the outline of the bone at this point. The forwardly 

 directed process from the squamosal beneath the lateral temporal 

 fossa does not reach the jugal and the lower margin of the opening 

 is com] leted by the quadrato-jugal. Both the quadrate and the 

 quadrato- jugal have \ een forced out of place, upward, to some 

 extent. A rugose area on the outer posterior surface of the lower 

 end " : tie jugal suggests that an epijugal may have been present. 



The orbit is higher than wide and slightly oblique, with the 

 greater diameter directed downward and forward. The supra- 

 orbital horn-core rises immediately above the eye-opening. 

 It is short and in right, and broadly oval in cross section near 

 the base, with the greater diameter fore and aft. Its basal outer 

 surface is flattened and lies in the same vertical plane as the 

 orl ital rim. Behind the horn-con- the postfrontal is tumid, 

 and between this convexity and the orbital rim the surface is 

 sunken. 



