268 MERISTIC VARIATION. [part I. 



Of (2), Simla satyrus No. 166, Dasyurus maculatus No. 385, 

 E. asinus No. 352. 



Of (3), Dog No. 257, Bettongia cuniculus, No. 392, Ateles margi- 

 natus No. 203, Phoca barbata No. 318, Ommatophoca rossii No. 320. 



Of these, further examples may be seen in the evidence given 

 regarding the anterior premolars of Galictis barbara, Meles, and 

 Hevpestes. 



(3) Division of Teeth. 



Among the cases of increase in number of teeth are many in 

 which by the appearances presented it may be judged that two 

 teeth in the varying skull represent one tooth in the normal, and 

 have arisen by the division of a single tooth-germ. 



Of such division in an incomplete form several examples have 

 been given. The plane of division in these cases is usually at 

 right angles to the line of the jaw, so that if the division were 

 complete, the two resulting teeth would stand in the line of the 

 arcade. Incomplete division of this kind is seen in the first 

 premolar of Ommatophoca rossii No. 320, in the fourth premolar of 

 Phoca groenlandica No. 324, in the incisors of Dogs No. 219, 

 in the canine of Dog No. 221, in the lower fourth premolar of 

 Dasyurus geojfroyi No. 383. The plane of division is not however 

 always at light angles to the jaw, but may be oblique or perhaps 

 even parallel to it, though of the latter there is no certain case. 

 Cases of division in a plane other than that at right angles to the 

 jaw are seen in C. vulpes No. 230, Phalanger orientalis No. 368, 

 Phoca groenlandica No. 326 and doubtfully in a few more cases. The 

 existence of the possibility of division in these other planes is of 

 some consequence in considering the phenomenon of duplicate teeth 

 standing 1 together at the same level in relation to that of the 

 presence of duplicate teeth in series. Beyond this also it may be 

 anticipated that if ever it shall become possible to distinguish 

 the forces which bring about the division of the tooth-germ, the 

 relation of the planes of division to the axis of the Series of Repe- 

 titions will be found to be a chief element. 



(4) Duplicate Teeth. 



Teeth standing at or almost at the same level as other teeth 

 which they nearly resemble may conveniently be spoken of as 

 duplicate teeth, though it is unlikely that there is a real distinc- 

 tion of kind between such teeth and those extra teeth which stand 

 in series. Duplicate teeth were seen in Felis domestica Nos. 286 

 and 287, Cams mesomelas No. 228, Hevpestes ichneumon No. 300, 

 [Putorius] Vison Jiorsfieldii No. 311, Helictis orientalis No. 312, 

 Cystophora cristata No. 322, and perhaps in some other cases. That 

 these cases are not separable on the one hand from examples of 

 extra teeth in series may be seen from Herpestes gracilis No. 2.99, 

 Cystophora cristata No. 321 [compare with No. 322], Brachyteles 



