23 



Measurements of type specimen. MM. 



Length of external face of crown 2-25 



Transverse diametei . . 2 ■ 50 



Length of interno-posterior face 3 30 



Maximum height of crown (height of metacone) I • 30 



The presence of an incipient hypocone is a decidedly progressive character, and one that 

 has been considered by Bensley"* in the Australian genus Perameles as an indication of a 

 change from an " insectivorous to an omnivorous condition." The hypocone appears not to 

 be present in the molars of Didelphys, and suggests that the Cypress Hills tooth may repre- 

 sent a distinct genus. Under the circumstances, however, with so little evidence to go on, a 

 provisional reference to the above, mainly Oligocene genus is at present adhered to. 



Another small tooth, plate VIII, figures 5-7, from the same locality as the above, deserves 

 attention. It possibly represents an undescribed genus of marsupial of the polyprotodont 

 section, but the one small tooth found is quite insufficient for any definite determination. The 

 crown is triangular in cross section, and consists of a high, apical, principal cusp, subpyramidal 

 in shape, with two less elevated, conical, subequal cusps occupying the base of the triangle. 

 The tooth has one root which would suggest an anterior premolar^ but the crown is molariform, 

 and presumably a posterior molar is represented. Eegarding the tooth as a lower molar, the 

 principal apical cusp is the protoconid, the smaller pair being the metaconid and paraconid 

 occupying internal posterior and anterior positions respectively. A cingulum is continuous 

 round the base of the crown except internally. Anteriorly, and externally, the cingulum is 

 feeble, but posteriorly it becomes accentuated, and ends abruptly beneath the posterior slope 

 of the metaconid in a minute tubercle. On the internal face of the crown a vertical furrow 

 occurs between the bases of the two smaller cusps. 



Measurements. MM. 



Maximum antero-posterior diameter of crown 1-20 



" transverse diameter of crown 1-50 



Height of external cusp (protoconid) 1 ■ 80 



" internal cusps (metaconid and paraconid) ■ 85 



The second lower molar of Notary ctes typhlops^, Stirling, has a cusp arrangement very 

 similar to that of the Cypress Hills tooth, suggesting that the dentition of this living Australian 

 marsupial may be primitive in some of its characters rather than specialized. In the Cypress 

 Hills tooth, however, the talonid is only indicated by a minute tubercle, or enlargement of the 

 cingulum at the base of the metaconid, proportionately much smaller than the definite sub- 

 sidiary cusp of Notoryctes. 



It is possible that this tooth, and the upper molar above described, both of the collection 

 of 1904, may belong to the same animal. 



* On the Evolution of the Australian Marsupialia ; with remarks on the relationships of the marsupials in general, by B, 

 Arthur Bensley, Ph. D., University of Toronto ; Trana. Linnean Society, vol. IX, part 3, 1903. 



* This tooth is described and figured by Dr. Bensley in his memoir of 1903, p. 119, pi. 6, figs. 17 a-h, 



