1886. ] On Lemurine Reversion in Human Dentition. 941 
ON LEMURINE REVERSION IN HUMAN DENTITION. 
BY- Es. D. COPE, 
EE ONS of the molar teeth of man, given by anato- 
mists, differ in important respects. Thus F. Cuvier (Dents 
des Mammifers) states that while the crown of the first superior 
true molar consists of four tubercles, those of the second and 
third superior true molars consist of but three tubercles. In the 
American edition of “Sharpey and Quain’s Anatomy” it is stated 
that the crowns of the superior true molars of man consist of 
four tubercles, and the same statement is made in Allen’s late 
work on human anatomy. 
My observations having shown me that both of these descrip- 
tions apply correctly to certain types of dentition, I determined 
to examine for myself to ascertain, it possible, the extent and 
value of the variations thus indicated. My interest in the subject 
had been especially stimulated by the researches among the ex- 
tinct Mammalia and the results which I had derived from them. 
These are in brief as follows: F irst, the quadritubercular type of | 
molar crown illustrated by the first superior true molar of man 
belongs to the primitive form from which all the crested upper 
(lophodont) molars of the hoofed placental mammals have been 
derived ; and second, this quadritubercular type of molar has 
itself been derived from a still earlier tritubercular crown by the 
addition of a cusp at the posterior internal part of it. This tri- 
tubercular molar in the upper series has given origin directly to 
the superior sectorial teeth of the Creodonta and Carnivora. In 
the inferior series I have shown that in known placental Mam- 
Malia, at least, the primitive molar crown is quinquetubercular or 
tritubercular with a posterior heel; that this form gave origin 
to the inferior sectorial tooth of Carnivora by modification; and 
> the quadritubercular type, corresponding to the superior quad- 
titubercular crown, by a loss of the anterior inner angle and cusp. 
And from the quinque and quadritubercular types of lower molar 
crown the various specialized types of the ungulates have been 
derived. 
Considerable significance, therefore, attaches to the question as 
o whether the superior true molars of Homo sapiens are quad- 
"tubercular or tritubercular. The inferior molars are also either 
Qadritubercular or quinquetubercular, but less significance at- 
S to this modification than to that of the superior true molars- 
