chap, ix.] TEETH : DASYURID^E. 257 



and small tooth having nearly the form and size of normal w^ 4 . 

 The lower series is alike on both sides, each having an extra 

 molar behind m 4 (Fig. 67, C). The two extra teeth are well formed, 

 being as long bnt not quite so thick as m*. B. M., 41, 12, 2, 3. 



In Cat. Marsup. Brit. Mus., 1888, p. 265, note, Thomas refers 

 to this skull, and describes it as an instance of an additional molar 

 inserted between m 3 and m 4 on the left side above and on both 

 sides below r . This view is of course based on the resemblance 

 that the extra m? of the left side bears to a normal "^ and on 

 the fact that the left ^ is like no tooth normally present. In 

 the light however of what has been seen in other cases of super- 

 numerary molars a simpler view is possible. For in cases in 

 which a supernumerary molar is developed behind a molar which 

 is normally a small tooth, the latter is frequently larger than 

 its normal size. In the present case it appears that on the right 

 side ? » 4 has been thus raised from a small tooth to be a tooth 

 of fair size, while on the left side the change has gone further, 

 and not only is m?_ promoted still more, but a supernumerary 

 irf_ is developed as well. It is interesting to note that this n& 

 is a small tooth, very like normal ^*, and it thus may be said 

 to be beginning at the stage which itf_ generally reaches. In 

 the lower jaw mF is added without marked change in m* ; for 

 m^ is normally a large tooth and has, as it were, no arrears to 

 be made up. Mr Thomas, to whom I am indebted for having 

 first called my attention to this remarkable case, allow T s me to 

 say that he is prepared to accept the view here suggested. 



Phascologale. In the upper jaw normally 3 premolars, by Thomas 

 reckoned as p\ p 3 and p*. Between the first and second ("p 3 ") there 

 is sometimes, but not always, a small space, and in the following case a 

 supernumerary tooth was present in this position. 

 !86. Phascologale dorsalis, (Fig. 68) having an extra premolar 

 between the first and second in the left upper jaw: rest normal. B. M., 

 1868, b. Thomas, 0. ± Phil. Trans., 1887, p. 447, PL 27, figs. 7 and 8. 



In the lower jaw J7 4 is often small and may be absent. As Thomas 

 has observed, the size of ]/ in the upper and lower jaws maintains a 



left 



right 

 reversed 





Fig. 68. Phascologale dorsalis, No. 386. Teeth of left upper jaw from canine 

 to first molar; below, the teeth of the right side reversed (after Thomas). 



B. 17 



