The Rise of the Mammalia in North America.¹II

Abstract

Primitive Trituberctilism. There is a very general tendency among the vertebrates as a whole, fishes and reptiles as well as mammals, to form what are called “triconodont” crowns by the addition of lateral cusps to simple cones. In the mammals alone, these three cusps pass into higher stages of evolution, through what is called “trituberculy,” in which these cusps form a triangle.