1893.] Zoology. 2 1015 
has stated the manner in which Kükenthal and Róse defend the theory 
that the complex dental crowns of the later Mammalia, are the result 
of the fusion of a number of primitive, distinct, simple reptilian teeth. 
Professor Osborn and myself have shown that the history of mammal 
dentition indicates the opposite process to have taken place; viz, the 
gradual accession of cusps to a simple primitive cusp, by a process of 
complication. . The well known fact that the dental cusps hecome 
more numerous and display greater modifications with the passage of 
geological time, is opposed to the idea supported by the authors cited. 
Dr. Röse has recently endeavored to explain’ the origin of the den- 
tition of the elephant. As is well known, the transverse crests are 
laminiform, and reach the number of twenty-three in the Elephas 
indicus. It is also well known that as we pass backward in time we 
find in the earliest known proboscidians, posterior molar teeth with 
only four, and even two transverse crests. This fact is one of many 
which distinctly negatives the fusion theory. Dr. Róse's explanation 
istruly extraordinary. He declares the complexity of the molar of 
Elephas to be due to a reversionary inheritance of a reptilian dentition, 
and fusion ofthe dental elements of the same. Thus the farther removed 
from the ancestral Reptilia we get, in time and in character, the stronger 
becomes the hereditary tendency! This seems to be the reductio 
ad absurdum of the theory. 
Dr. Forsyth Major makes an interesting contribution to the subject. 
in a paper in the Proceedings of the London Zoological Society,’ on 
the dentition of the Sciuride. He announces his disbelief in the trit- 
ubercular origin of the placental mammalian dentition, and supports 
the view that all the forms, including the tritubercular, are the descen- 
dents of a multitubercular type, as now found in the Multituberculata. 
He believes that the superior molars of the squirrels support his con- 
tention, as he thinks that he can trace them better from a multituber- 
cular than from a tritubercular origin. . 
I have stated as is my belief, as long ago as 1883, that the Glires 
were descended from the Tillodonta, and no reason has since appeared 
to invalidate this opinion. It was strikingly confirmed by the dis- 
covery that there were no Glires in the Puerco fauna, while Tillodonta 
are not rare. In the Tillodont dentition we have all the materials 
necessary for the evolution of the glirine dentition along the usual 
!Morphologischen Arbeiten von Schwalbe, Strassburg i. E., 1893, p. 173. 
?Proceeds. Zoolog. Sci. London, 1893, p. 179. 
*Extinct Rodentia of North America, Anitan NATURALIST, p. 380; Op. cit. 
1885, p. 347 more definitely. 
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