Cowan (Canad. Jour. Res., D , 24: 71–103) states that “variations in numbers of teeth in the genus Odocoileus are rare.” He further reports but one instance of supernumerary incisors in Odocoileus hemionus and quotes two cases of canines encountered by Nordquist (Calif. Fish and Game, 27(1): 39–40). Because of this apparent rarity of variations in number of teeth the writer is reporting on four cases of fewer teeth than normal and four cases of more than normal which he has encountered among Rocky Mountain mule deer, O. h. hemionus , of Utah and eastern Nevada. Fewer than normal deciduous or permanent teeth .—Case 1 involved a 28-month-old doe with all permanent premolars functional except the first one (P2) of the left mandible, where a tiny milk tooth 2 mm. in height and in diameter was still retained. Removal of the underlying bone revealed no corresponding permanent tooth. …