. On the anatomy of vertebrates [electronic resource] . of the caninesand the concomitant break or < diastema in the dental series forthe reception of their crowns when the mouth is shut. This ismanifested in Gorillas, Chimpanzees and Orangs, together withthe sexual difference in the proportions of the canine teeth. Thencomes the added premolar in the New World Monkeys, fig. 251, HOMOLOGIES OF TEETH. 377 p 2, and the further additions in lower quadrupeds, until in theHog genus we see the old primitive type of diphyodont dentitionresumed or retained. In the genus Sus, fig. 293 illustrates th
. On the anatomy of vertebrates [electronic resource] . of the caninesand the concomitant break or < diastema in the dental series forthe reception of their crowns when the mouth is shut. This ismanifested in Gorillas, Chimpanzees and Orangs, together withthe sexual difference in the proportions of the canine teeth. Thencomes the added premolar in the New World Monkeys, fig. 251, HOMOLOGIES OF TEETH. 377 p 2, and the further additions in lower quadrupeds, until in theHog genus we see the old primitive type of diphyodont dentitionresumed or retained. In the genus Sus, fig. 293 illustrates the phenomena of de-velopment which distinguish the premolars from the molars. Atthe stage exemplified the first premolar,1 p l, and the first molar,m l, are in place and use, together with the three deciduousmolars, d 2, d 3, and d 4 ; the second molar, m 2, has just begunto cut the gum; p2,p3, and p 4, together with m 3, are more orless incomplete and concealed in their closed alveoli. The premolars displace deciduous molars in order to rise into 294. Deciduous and permanent teeth (Sits). Lower jaw place; the molars have no such relations ; it will be observed,that the last deciduous molar, d 4, has the same relative supe-riority of size to d 3 and d 2 which m 3 bears to m 2 and m l; andthe crowns of p 3 and p 4 are of a more simple form than those ofthe milk-teeth which they are destined to succeed. The premolars have a more simple structure as well as smallersize, than the true molars, in all Artiodactyles. In the Ru-minants they represent only the moiety of the true molars, orone of the two semi-cylindrical lobes of which those teeth consist,with, at most, a rudiment of the second lobe. The Perissodactylesare distinguished by the size and complexity of more or less ofthe premolars. In Equus, p 2, p 3 and p 4, even exceed in sizem l, jb2 and m 3. In Rhinoceros and Palceotherium the propor-tions of the molars and premolars are reversed; but the struc-ture is the same. In Lophi
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