118 INTRODUCTION. 



form huge tusks : those of the upper jaw, though of considerable thickness, 

 are short and blunt, being worn by the canines of the lower jaw, which 



curve upward with a bold sweep, and are of 

 great weight and thickness. On the con- 

 trary, among many of the Insectivora, and 

 in the Galeopithecus, as also in the lower 

 jaw of the Lemurs, the canines are at their 

 minimum ; and it is only with reference to 



position that they claim the appellation. In 

 / It I Iff ..^> \ugrr * , j; 1 



/ jf I if the Aye-aye there are no canines. 



The molar teeth differ materially in 

 character and in number in different ani- 

 mals, bearing immediate reference to the 

 nature of their food. They are usually 

 divided into two groups ; namely, true 

 ; of the Morse. molars, and false molars. The false molars, 



where present, follow the canines, and are not only smaller than the true 

 molars, but of a different shape : they are either bicuspid, as in Man and 

 the Simiae ; or unicuspid, as in the Dog : their number in the Carnivora 

 never exceeds three on each side, in each jaw, excepting on the lower 

 jaw of Canis Megalotis, which has four. 



The true molars are infinitely diversified. In Man and the Simiae 

 they exhibit a uniformity among each other, and have four tubercles on 

 their grinding surface ; excepting the last molar of the lower jaw in cer- 

 tain genera of the Simiae, which has five tubercles. In the Insectivora 

 they are crowned with acute tubercles, or conical points, more or less 

 elevated ; the Mole affords a good specimen of acutely tuberculated 

 grinders. In some of the Seals the molars are simple and conical ; in 

 others, they are divided into three pointed tubercles ; in others, again, 

 they are slightly three-lobed. In the Rodentia there are no false molars, 

 and the true molars are mostly laminated ; in ruminants, and in the 

 Horse and Elephant, there are no false molars ; and the molars, when 

 worn, also display a laminated structure.* 



In the Edentata, the molars, where present, are simple and cylindrical. 

 In the Carnivora the molars are divided into false, carnivorous (carnas- 

 sieres), and tuberculous molars ; the number of the latter diminishing 

 according to the sanguinary habits of the species. The carnassiere,-}- or 

 carnivorous molar, succeeds the last false molar, and forms, as it were, 

 the base, upon which rests the anterior part of the zygomatic arch ; or, in 

 other words, a line following the curve of this arch will bisect the middle 



* The laminae of compound teeth are disposed either transversely, longitudinally, or obliquely, and 

 present various forms as of a trefoil in the Hippotamus ; of crescents in the ruminants ; of triangles 

 and irregular folds in the rodents. 



t The carnassiere really belongs to the false series. 



