108 
NOTES ON THE TEETH OF NOTOTHERIUM MITCHELLI. 
No. L— VARIATION IN THE UPPER PERMANENT PRE- 
MOLAR OF NO TO THE 7? 1 TJ 21 MITCHELLI , OWEN. 
By L. Glauicrt, W.A. Museum, Perth. 
(Lead on 14 tJi June, 1921.'*') 
The permanent Premolar tooth of diprotodont marsupials, the 
only replacing number of the dental series, is most important for 
diagnostic purposes, it alone being sufficient for the determination 
of many species. 
It is therefore of interest to describe a variation noticed among 
the remains of Nototherium 2Iitchelli collected in the Mammoth 
Cave, Margaret River, in the extreme South-West of this State. It 
must be remarked that the associated lower permanent premolars do 
not show a corresponding range of variation from the type. 
The tooth is described by Professor Owen in the following 
terms: — “The first upper molar ( cl' 1 ) may be said to be two-1 abed, 
but it is divided in an opposite direction to that in the rest of the 
series, viz., into an outer and an inner, rather than a front and a 
back lobe. The working-surface is sub-triangular in form, the angles 
obtusely rounded, measuring in fore-and-aft extent 1 inch 1 line in 
the male Nototherium Mitehelli / the transverse diameter, posteriorly, 
is 11 lines. 
The outer lobe or division is the chief one, and constitutes the 
outer two-thirds and the whole fore-and-aft extent of the tooth; the 
outer side of its base swells out like part of a cingulum or ridge; the 
summit is sub coin pressed, and seems to have been trituberculate ; the 
inner and lower divisions consist of a larger hind tubercle and a 
smaller front one ; it is implanted by two roots, one behind 
the other, the posterior being the largest and grooved anteriorly, as 
if preparatory to further transverse subdivision.” t 
The Mammoth Cave specimens supply a series of ten upper 
premolars in all stages of wear, including teeth that have just re- 
cently come up into line, as well as others that have been in use for 
some considerable time. 
* By permission of the Trustees of tlie Museum, 
t Phil. Trans. Hoy. Soc., 1872, page 67. See also Extinct Mamin., Aust.,l8<<, 
Vol. I., page 275. 
