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Sometimes it is very prominent in man, as it is in most apes and many of the other mammals, and forms a sort of tusk. The apes of the Old World, or all the living or fossil apes of Asia, Africa, and Europe, have the same dentition as man. Skeletons of man and the four anthropoid apes. On the other hand, all the American apes have an additional pre-molar in each half of the jaw.
Natural size. b. The second mammiferous genus discovered in the same slates was named originally by Mr. It manifests a much stronger likeness to the marsupials in the general form of the jaw, and in the extent and position of its inflected angle, while the agreement with the living genus Didelphys in the number of the pre-molar and molar teeth is complete.
The first, or most anterior pre-molar of the lower jaw has one predominant cusp or cone; the second, like both in the upper jaw, is "bicuspid," or bi-tuberculate, as in man.
A striking peculiarity of their dentition, one in which they differ from all other quadrupeds, consists in their having a single large pre-molar, the enamel of which is furrowed with vertical grooves, usually seven in number. Plagiaulex Becklesii, Falconer. Middle Purbeck. Right ramus of lower jaw, magnified two diameters. a. Incisor. b, c. Line of vertical fracture behind the pre-molars. pm.
The Cebidae have thirty-six teeth; the Marmosets possess but thirty-two: three of them, however, are pre-molar, as are three of those of the Cebidae, thus distinguishing them both from all the forms of the Old World.
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