44 ] 
RECORDS OF W.A. MUSEUM. 
two parallel lobes are a striking feature in the premolar of Diprotodon 
and can be seen in every figure. As they are not present in the 
Mammoth Cave premolar, it is impossible to regard this tooth as 
belonging to this genus. 
Premolars of Notothenmu as well as the upper premolar of 
Macleay’s Zygomaturus trilohus, are figured by De Vis in the same 
volume.^ The Mammoth Cave premolar is unlike the Nototherium 
or Owenia^ teeth shown, and differs from the Zygomaturus tooth in 
the absence of the posterior cusp. In fact, the tooth has a 
triangular outline like N . iiierme shown in figure 5, plate xmi., of 
Owen’s “Extinct Mammals of Australia,” which it resembles more 
than the other Notothenmu premolars shown on plate lxxxviii., 
figures 11-17, 01' miniature on plates xxxvi. and xxxvii., or in full 
size in figures 3 and 4, plate XLiii. It differs, however, from Owen’s 
N . inernie in several important points. This author describes the 
upper premolar of that species as follows, on p. 277. The tooth 
“ is relatively smaller and less complex on the grinding surface than 
in the corresponding tooth in N mitchelli, the transverse and antero- 
posterior diameters are alike. The outer lobe or division has one 
coronal prominence upon which a slender triangular tract of dentine 
is exposed on the shorter, inner lobe ; an anterior and a posterior 
basal ridge bounds corresponding depressions divided by the con- 
fluence of the apices of the outer and inner divisions at the centre 
of the crown ; a short external basal ridge closes the concavity 
impressed upon the hind half of the outer surface of the crown. 
Owen described (loc. cit., p. 275) the tooth D3 of the upper jaw of 
N. mitchelli in the following terms. The tooth “ may be said to be 
two-lobed, but 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 . . . 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-compressed and seems 
to have been tritubercnlale ; the inner and lower division consists 
of a larger hind tubercle and a smaller front one It is 
r Proc, Royal Soc. Queensl., Vol. V., 1888, p. in, et seq., and plate , 1S89. 
Renamed “ Eiiovvenia,” as “Owenia” was previously occupied. 
