"Breadth of rostrum above Premolars" is easily duplicated in Lepus but in Sylvilagus the control points are difficult to find.
"Mammals Obtained by Dr. Curt von Wedel from the Barrier Beach of Tamaulipas, Mexico"
E. Raymond Hall
They are inhabitants of the old world; they all have the same number of teeth as man, possessing four incisors, two canines, four Premolars, and six true molars in each jaw, in the adult condition, while the milk dentition, as in man, consists of twenty teeth,-four incisors, two canines, and four molars in each jaw.
"Thomas Henry Huxley; A Sketch Of His Life And Work"
P. Chalmers Mitchell
It is further noteworthy that in a case where there is no diminished use of the jaws, but where they have been shortened by selection, a like want of concomitant variation is manifested: the case being that of the bull-dog, in the upper jaw of which also, "the Premolars ...
"Essays: Scientific, Political, & Speculative, Vol. I"
Herbert Spencer