HOMOLOGIES OF TEETH. 373 



size and shape, Cuvier felt himself compelled to discard from the 

 series of false molars, but which we now see is proved by its 

 developmental relations to d 4, as well as by its relative position 

 and similarity to p 4 in the lower jaw, fig. 292, n., Ursus, to be 

 veritably the last of the premolar series, and to agree not in 

 shape only, but in every essential character, with the three pre- 

 ceding teeth called by Cuvier ( fausses molaires.' So, likewise, in 

 the lower jaw, it is seen that the primitive deciduous series, fig. 263, 

 d i, d 2, d 3, and d 4, will be displaced by the corresponding pre- 

 molars, p i, p 2, p 3, p 4 ; and that the tooth in i, called car- 

 nassiere by Cuvier, in the lower jaw, differs essentially from that, 

 p 4, so called in the upper jaw, by being developed without any 

 vertical predecessor or deciduous tooth. 



The same law of development and succession prevails in the 

 genus Canis as may be readily seen in the jaws of a dog of ten 

 months' age. Although the tooth, m i, in. fig. 293, in the 

 lower jaw has exchanged the tubercular for the carnassial form, 

 it is still developed, as in the Bear, behind the deciduous series, 

 and independently of any vertical predecessor, fig. 262, m i ; and 

 the tooth, ib. /> 4, above, although acquiring a relative superiority of 

 size to its homologue in the Bear, and more decidedly a carnassial 

 form, is not the homotype of the permanent carnassial below, but 

 of that premolar, p 4, which displaces the deciduous carnassial, 

 d 4. The symbols in fig. 293, m., sufficiently indicate the re- 

 lations of the other teeth, and the conclusions that are to be 

 drawn from them as to their homologies. 



In the genus Felis, fig. 260, the small permanent tubercular 

 molar of the upper jaw, m i, has cut the gum before d 4 has been 

 shed ; but though analogous in function, this tooth is not homo- 

 logous with, or the precedent tooth to m i, but precedes the 

 great carnassially modified premolar, p 4. In the lower jaw the 

 tooth, m i, which is functionally analogous to the carnassial 

 above, is also, as in the Dog, the first of the true molar series, 

 and the homotype of the little tubercular tooth, m i, above. 

 And the homologues of the permanent teeth, p 4 and m i below, 

 fig. 293, Y., with those so symbolised in the Dog, ib. m., teach 

 us that the teeth which are wanting in the feline, in order to 

 equal the number of those in the canine dentition, are m 2 in 

 the upper jaw, m 2 and m 3 in the lower jaw ; p i in the upper 

 jaw, p i and p 2 in the lower jaw ; thus illustrating the rule, that, 

 when the molar series falls short of the typical number, it is from 

 opposite extremes of such series that the teeth are taken, and that 

 so much of the series as is retained is thus preserved unbroken. 



VOL. III. *B B 3 



