908 



TEETH. 



culeuse" (my m. 3), and not any of the 

 four false molars. The true second tuber- 

 cular above (m. 2) is, however, so much de- 

 veloped in the bear as to oppose both m. 2 and 

 .%. 3 in the lower jaw, and it might seem to 

 Include the homotypes of both those teeth 

 coalesced. One sees with an interest such as 

 only these homological researches could ex- 

 cite, that they were distinctly developed in 

 the ancient Amphicyon (fig- 576.), which ac- 

 cordingly presents the typical formula. Thus, 

 I repeat, the study of the relative position of 

 the teeth of the bear might have led to the 

 recognition of their real nature and homolo- 

 gies, and have helped to raise the mask of their 

 extreme formal modifications, by which they 

 are adapted to the habits of the more blood- 

 thirsty Carnivora. But the truth is plainly 

 and satisfactorily revealed when we come to 

 trace the course of development and succes- 

 sion of these teeth. The weight which must 

 ever attach itself to an opinion sanctioned by 

 the authority of both the Cuviers, demands 

 that a conclusion contrary to theirs, and 

 which seems to be opposed by Nature herself 

 in certain instances, should be supported by 

 all the evidence of which such conclusion is 

 susceptible. 



I proceed, therefore, to show how, in the 

 bear, my determinations of the teeth are es- 

 tablished by their development, as well as by 

 their relative position. As the question only 

 concerns the molar series, the remarks will be 

 confined to these. In the jaws of the young 

 bear, figured in cut 581 ., the first premolar, p. 1, 

 is the only one of the permanent series in place ; 



similarity to p. 4 in the lower jaw (fig. 581, 

 URSUS), to be veritably the last of the pre- 

 molar series, and to agree not in shape only, 

 but in every essential character, with the 

 three preceding teeth called by Cuvier 

 "fausses molaires." So, likewise, in the lower 

 jaw, we see that the primitive deciduous 

 series, d. 1, d. 2, d. 3, and d. 4, will be displaced 

 by the corresponding premolars,/>. l t p. 2, p. 3, 

 and p. 4 ; and that the tooth m. 1, 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 succes- 

 sion prevails in the genus Canis {fig. 582.). 

 Although the tooth m. 1 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 indepen- 

 dently of any vertical predecessor; and the 

 tooth p. 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 carnas- 

 sial below, but of that premolar (p. 4) which is 

 destined to displace the deciduous carnassial 

 d. 4. The symbols sufficiently indicate the 

 relations of the other teeth, and the conclu- 

 sions that are to be drawn from them as to 

 their homologies. It is interesting to observe 

 in the deciduous, as well as in the permanent 

 series, that the lower carnassial d. 4 is not the 

 homotype of the upper one d. 3, but of the 

 tooth which Cuvier calls the " tuberculeuse 

 du lait," d. 4 in the upper jaw. 



Deciduous and permanent dentition of the Sear (Ursus). 



the other grinders in use are the deciduous 

 molars, d. 2, d. 3, and d. 4 ; d. 2 will be displaced 

 by p. 2, d. 3 by p. 3, and d. 4 by the tooth p. 4, 

 which, notwithstanding its 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 



In the genus Felis (fig. 580.), the small per- 

 manent tubercular molar of the upper jaw, m. 1, 

 has cut the gum before its analogue d. 4 of 

 the deciduous series has been shed ; but 

 though analogous in function, this is not ho- 

 mologous with, or the precedent tooth to m. 1, 

 but, as in the dog, to the great carnassially 

 modified premolar, p- 4-. In the lower jaw the 



