FORM. 299 



with which the foregoing kinds of teeth are recognizable in the Mam- 

 niahan genera, to indicate them by an abbreviated formula of the 

 initial letters, or first syllables of their respective denominations ; 

 thus, / or in. signifies incisor ; c or can. canine ; p or prem. premolar ; 

 m or mol. molar: succeeding numerals, according to their relative 

 position to added lines, give the number of these several kinds of 

 teeth on the right and left sides of the upper and lower jaws. For 

 example, the dental formula of the genus Homo is : — 



Incisors — : canines — : premolars — ; molars — ^ : = 32. 



2-2 ' 1-1 ' ^ 2-2 ' 3-3 



which expresses that, on each side of both upper and lower jaws, 

 there are two incisors, one canine, two premolars, and three true 

 molars ; thirty-two in all. 



The last upper premolar and the first lower true molar in the 

 Carnivora are termed, from their peculiar form, * sectorial' or * car- 

 nassial' teeth, ' molaires carnassieres' of Cuvier. Teeth of an elon- 

 gated conical form, projecting considerably beyond the rest, and 

 of uninterrupted growth are called ' tusks ;' such are the incisors 

 of the Elephant and Dugong, 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 pectinati.' The canines of the Baboons are deeply 

 grooved in front, like the poison-fangs 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, ' dentes 

 serrati.' 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 indented 

 laterally by opposite longitudinal grooves, as to appear to be com- 

 posed of two cylindrical teeth cemented together, 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 



