CHAP. IX.] 



TEETH : DASYURID^E. 



257 



386, 



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 but 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. This view is of course based on the resemblance 

 that the extra »»? of the left side bears to a normal mt and on 

 the fact that the left w 4 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 ««* promoted still more, but a supernumerary 

 ra 5 is developed as well. It is interesting to note that this ft& 

 is a small tooth, very like normal ^_ 4 , and it thus may be said 

 to be beginning at the stage which m^ generally reaches. In 

 the lower jaw wf is added without marked change in ~m± ; for 

 mF 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, allows 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. 



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, O., Phil. Trans., 1887, p. 447, PL 27, figs. 7 and 8. 



In the lower jaw ~jfi is often small and may be absent. As Thomas 

 has observed, the size of p 4 in the upper and lower jaws maintains a 



left 



ri/fht 

 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 



