1897.] Trituberculy : 1005 
pressed and that the pair of outer cusps, paracone and meta- 
cone, persisted on their high primitive level; the crown being 
thus prepared for the transformation into the true “ sectorial.” 
But in the omnivorous and herbivorous types, all three 
cusps are depressed and the upper molars always increased 
their crushing area by the addition of a heel or “talon,” ex- 
actly analogous to that previously developed upon the lower 
molars. As is well known, this “hypocone” is an upgrowth 
from the cingulum and its typical mode of development is 
well shown in the Primates (Fig. 9). While this was going 
on, the trigon was also supplementing its bunodont equipment 
Fig. 9.—Superior molars of Primates, Anaptomorphus to Homo, showing 
evolution of hypocone, hy, from the cingulum, 
by the addition of the little intermediate cusps “ protoconule ” 
and “metaconule.” These always appeared where the “ tal- 
onid” abuts against the “trigon.” Thus, finally, the upper 
molar, like the lower, was provided with six cusps and both 
were ready to diverge into any ungulate form. 
All these foregoing stages persist and may be readily stud- 
ied and verified among some of the living marsupials, insecti- 
vores, lemurs and monkeys, and can be seen in any well- 
equipped osteological museum almost as well as among the 
fossil series. 
THE NOMENCLATURE OF THE MOLAR CUSPS AND CRESTS. 
The system proposed by the writer some years ago has now 
been adopted by many of the American, English and German 
writers who are studying the fossil series. It is based upon 
simple principles : 
1°. The termination “ -cone” is employed for all the primary 
central cusps derived from the crown of the tooth, while the 
