72 
Æ i PR Thus we get a quadricuspid tooth 
IV VI . IV VI above and below (the common buno- 
U n v te V ØE. dont type of Suidae, Primates etc.), 
but the cusps are 4+—5—6—7 above, 
2—3—4—5 below. Due to differences in food and grinding move- 
ments some of the cusps may be enlarged, others may be suppressed, 
connecting ridges and crests or less constant cusplets may be devel- 
oped (Ungulates), but the fundamental form of the tooth can 
always be traced back to the 7-cuspid (upper) or 5-cuspid (lower) 
tooth of the primitive types. It is only in very rudimentary tecth 
such as those of Odontoceti, Pinnipedia, Edentata a. 0. that the 
fundamental pattern is totally effaced. — This is the first time 
that a theory has not only tried to give but has worked out a 
clear, palæontologically well-founded plan, showing the differentia- 
tions of thé mammalian teeth since the origin of this vertebrate 
class, indicating their causes and giving the homology of the cusps 
of the different tooth-types. 
1883 Magitot takes up again Gaudry's theory that the 
mammalian teeth are composed of several conical teeth: ,,La forme 
initiale des dents est le cone. C'est le type primordial, Vunité 
dentaire. Les formes les plus complexes des organes dentaires 
peuvent se réduire par l'analyse en un nombre variable des éléments 
primordiaux ou unités, réunis par voie de coalescence." (pag. 88). 
He finds the proof in the following: ,,Le bulbe dentaire, en effet, 
est primitivement composé d'une base conoide qui persiste ainsi 
pendant les premiéres phases de Vévolution ... Sur cette base pri- 
mitive apparaissent des saillies en nombre égal aux tubercules de 
la couronne future." (pag. 36). By the coalescence of these 
"gaillies” (outgrowths) the crown is formed. If this is intended to 
be large, their number is increased, if small, their number is 
reduced. The incisors start with three cusps, though the crown 
apparently is unicuspid; therefore they must be reduced, whereas 
the canine has preserved the primordial type. He speaks mostly 
