745 
The elevated primitive triangle (Trigon) with a primitive cutting, 
piercing or sectorial function. 
The depressed heel (Talon), with a primitive crushing or grinding 
function, 
In the earliest stages the upper and lower molars were simple 
triangles of cusps, aS in the modern Cape Mole, Chrysochloris. 
The lower molar had the apex (protoconid) turned outwards and the 
base (para- and metaconids) turned inwards, while the upper molar 
had these relations reversed. As shown in the accompanying diagram, 
Figure 2, the opposition of these triangles makes a perfect cutting 
mechanism, and as CopE has shown this is effective at every stage of 
development. If the protocene were at the outer angle of the upper 
molars, it is impossible to conceive of an effective series of inter- 
mediate stages. 
The first step towards the crushing function is the development 
of the hypoconid upon the incipient talonid which is later reinforced 
by two more cusps, the entoconid and hypoconulid. Thus the en- 
tire heel or talonid is complete upon the lower molars 
before it commences to develop upon the upper molars, 
as shown in Anaptomorphus (Fig. 1, 7 and Fig. 3, 9) as well as 
in the ontogeny. 
Upon the upper molars the talon is only developed in bunodont 
types, such as the Primates and Ungulates, to still further increase 
the crushing area of the crowns; it always arises as seen in the 
talonia: 
Lower molar. Upper and lower molars opposed. Upper molar. 
Fig. 2. Key to Plan of Upper and Lower Molars in all Mammals. Each tooth 
consists of a triangle, trigon with the protocone, pr at the apex. The apex is on the 
inner side of the upper molars and on the outer side of the lower molars. 
