148 I' a in rsity of California Publications in Zoology [Vol. 10 



nelsoni this is approximately triangular, with the orbital angle 

 less than a right angle; furthermore, this corner is produced far 

 down onto the forehead. Id sierrae the form in cross-section 

 is more nearly circular, with the orbital and medial angles both 

 obtuse and neither cornel? produced. The condition of the 



Fig. I. OvU cervina nelsoni, no. 4740: right horn, as viewed directly 

 towards orifice, anterior edge at top; upper left hand corner is the orbital 

 angle; note distinct triangularity of outline, with orbital angle acute. X %. 



Pig. :;. The same horn viewed from directly behind, across orifice; 

 note production of corner at orbital anjjle. X x /->. 



Pig. 2. Ovis cervina sierrae, no. 16360: right horn as viewed directly 

 towards orifice, anterior edge at top; note rounded outline with upper 

 angles both obtuse. X V-i. 



Fig. 4. The same horn viewed from directly behind, across orifice; 

 Bote evenly balanced outline, neither corner being produced. X Vi- 



