18 The Ottawa Naturalist. [April 



Mr. Charles H. Sternberg, are of two individuals to which the 

 writer has lately referredf in describing the integument of the 

 species. With one of these specimens the skull reproduced in 

 plate I is preserved. Part of another skull (collection of 

 1913), found separately, assists in elucidating the characters 

 displayed by the more perfect skull, and provides additional 

 evidence regarding some of those elements to whose great 

 development is mainly due the surprising shape of the head of 

 this species. 



The skull of Stephanosaurus rises to a great height in front 

 of and above the eye opening. In recently describing Grvpo- 

 saurus, also from the Belly River formation of Alberta, 

 the writer commented on the anterior depth of the skull 

 occasioned by the height to which the nasal rose. In the skull 

 of Stephanosaurus, however, the height attained by the nasals 

 is proportionately twice as great as in Gryposaurus; the depth 

 of the skull above its midlength is equal to its total length. 

 Viewing the skull from the side, the facial outline is sigmoid, 

 at first concave, ascending rapidly from the front until it is 

 vertical, whence it continues upward and reaches a point directly 

 above by an even convex curve ; this, the highest point preserved 

 in the specimen, is vertically above the midlength of the skull. 

 The general slope of the head behind is rapidly downward to the 

 squamosal, but as this part of the specimen is imperfect, the exact 

 outline is unknown. The almost vertical quadrate and the 

 sinuous horizontal contour of the slender mandible below com- 

 plete the profile of the head. 



The orbit is small and its centre is below the midheight of 

 the skull. 



The enlargement of the skull in front of and above the orbit 

 is due to the great development mainly of the prefrontal and 

 nasal bones, the latter of which rises upward in front of the pre- 

 frontal and passes backward over it and beyond it. This ex- 

 tension of the nasal beyond the upper limit of the prefrontal 

 appears to be supported from below by the frontal, although 

 this last bone has not been satisfactorily recognized. Above 

 the prefrontal and the supposed frontal, the nasal points almost 

 directly upward. In the speciinen its upper termination has 

 been broken off, but it probably formed with the other nasal a 

 stout spine somewhat of the shape suggested by the dotted 

 outline in the figure. 



The prefrontal is a large triangular bone with its base rest- 

 ing for the most part on the lachr3'mal, which latter is long and 



t The Ottawa Naturalist, Vol. XXVII, No. 10, January, 1914. rfA/^ ^ 



LIMRAR 



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