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teeth shows us also that his ""stereometric forms” are rather 
artificial. 
The Cope-Osborn-Scott-theory is the most commonly adopted 
one, and it seems also to be proved by much palæontological evi- 
dence. But if more carefully examined it presents some weak 
points. Its most important point is the identification of. the rep- 
tilian cone which is supposed to have rotated inwards above, out- 
Wards below. Against this assertion most of the attacks are directed, 
especially from the various embryogenetic. theories; but Osborn 
repels them all by referring to such palæontological series as Tri- 
conodon-Dryolestes, Peralestes, Kurtodon or others, where the rep- 
tilian cone is first seen as the median one of the three cusps and 
is finally rotated. But Osborn has still to give us irrefutable 
proof, 19 of the Triconodon-like forms being the ancestors of Dry- 
olestes etc., 29 of the supposed protocone and protoconid of these 
mammals really being homologous with the median cusp of Tri- 
conodon, One can hardly imagine how such a rotation could take 
Place; and if Gidley is right in his interpretation of the molar- 
Cusps of Dryolestes, the rotation has not taken place, but the so- 
called protocone is a secondary acquirement, the true protocone is 
still to be sought in the central one of the three outer cusps. If 
this holds good the whole. nomenclature and theory of Osborn falls 
to the ground; neither protocone nor protoconid are then identical 
With the reptilian cone. Certainly the anterior and posterior cusps 
of the lower molars of Spalacotherium, Tinodon, Menacodon etc. 
have grown a little inwards, but that these very forms should be 
the origin of the later tritubercular molar-type is not at all proved. 
The. para-, meso- and metastyle are considered as unimportant 
ACCessory Cusps by Osborn; therefore he will have difficulty in 
explaining their occurrence in usually the most primitive forms 
among widely divergent orders. — For the rest Osborn's identification 
of the same cusp of different mammalian molars is sometimes very 
doubtful. The teeth of the insectivores cause difficulties just be- 
Cause the three outer Cusps are considered as of secondary nature. 
Vidensk. Meddel. fra Dansk naturh. Foren. Båd. 65. $ 
