368 NOTICES OF THE MEETINGS [Feb. 10, 
Molar teeth, which are adapted for mastication, have either 
tuberculate, or transversely ridged, or flat summits, and usually 
are either surrounded by a ridge of enamel, or are traversed by 
similar ridges arranged in various patterns. Certain molars in 
the Dugong, the Mylodon, and the Zeuglodon, are so deeply in- 
dented laterally by opposite longitudinal grooves, as to appear, 
when abraded, to be composed of two cylindrical teeth cemented to- 
gether, and the transverse section of the crown is bilobed. The 
teeth of the Glyptodon were fluted by two analogous grooves on 
each side. The large molars of the Capybara and Elephant have 
the crown cleft into a numerous series of compressed transverse 
plates, cemented together side by side. 
The modifications of the crown of the molar teeth are those 
that are most intimately related to the kind of food of the animal 
possessing them. Illustrations were given of the chief of these 
modifications in the purely Carnivorous mammals, where the 
molars are simple, trenchant, and play upon each other like scissor- 
blades: in the mixed feeding species where the working surface 
of the molars is flattened or tuberculated: in the insectivorous 
species where it is bristled with sharp points: and in the purely 
herbivorous kinds, where the broad grinding surfaces of the teeth 
are complicated by folds and ridges of the enamel entering the 
substance of the tooth: the most complex forms being presented 
by the Elephants. 
Teeth of each of the kind above determined, and arbitrarily 
named “incisors,” “ canines,’ ‘‘ molars,’ have received other 
special names, in regard to certain peculiarities of form or other 
property ; and the ablest comparative anatomists have been led 
astray in determining their homologies when they have suffered 
themselves to be guided exclusively by morphological characters. 
The small anterior grinding teeth in the human subject have been 
called “ bicuspids.”” The penultimate upper tooth and the last 
lower tooth in the Lion are termed, from their peculiar form, 
“ sectorials,” or ‘‘ carnassial teeth,” ‘‘ molaires carnassitres’’ of 
Cuvier. Teeth of an elongated conical form, projecting consider- 
ably beyond the rest, and of uninterrupted growth, are called 
“* tusks ;’ such are the incisors of the Elephant and Dugong, and 
the canines of the Boar and Walrus : the long and large incisors of 
the Rodents have been termed, from the shape and structure of 
their cutting edge, scalpriform or chisel-teeth, ‘‘dentes scalprarii.” 
The inferior incisors of the flying Lemurs (Galeopithecus) have the 
crown deeply notched like a comb, and are termed “‘dentes pecti- 
nati.” The canines of the Baboons are deeply grooved in front, 
like the poison fangs, ‘‘ dentes canaliculati,” of some serpents. 
The compressed conical crowns of the molar teeth of the small 
clawed seals, Stenorhynchus, are divided either like a trident into 
three sharp points, or like a saw, into four or five points; the 
molars of the great extinct Zeuglodon had a similar form ; such 
