1006 The American Naturalist. [December, 
diminutive -conule is employed for the smaller “ intermediates ” 
or cuspules. . 
2°. All peripheral cusps or elements developed mainly from 
the cingulum or external borders of the crown are distin- 
guished as -styles (“ pillar” or “ buttress”). The only exception 
is the “hypocone,” which, while arising from the cingulum, 
soon takes its place upon the crown. 
3°. The crests, transverse and longitudinal, are always com- 
posed of two or more cusps and styles, and are distinguished 
by the termination -loph. 
4°. The prefixes “ proto-,” “ para-,” “ meta-,” “ hypo-,” “ ento-,” 
etc., refer back to the primitive position or order of develop- 
ment in the triconodont and tritubercular stages. 
5°. The suffix -id is employed arbitrarily to distinguish the 
elements of the lower molars from those of the upper. 
» 2) 6 
\ 
e 
LA 
` 
N 
\ 
` 
` 
ene y 
i \ s ' 
metalophid  hypolophid  hypoconntid metalophid hypolophid Av 
Teir Lophiodon 
Type. Type. 
Fig. 10.—MODELLING oF THE Cusps. 
The use of the terms “ trigon ” and “ talon ” for the cutting 
and crushing regions of the crown, respectively, is especially 
„advantageous among the the upper Mesozoic and lower Caino- 
zoic mammals, where it is necessary to refer constantly to the 
