126 Proceedings of the Royal Society of Victoria. 



Margin coarsely denticulate, with a broad shallow sinus at the 

 anterior end, otherwise almost perfectly flat ; but close examina- 

 tion, when placed on a flat surface, shows a very slight lateral 

 elevation, which is greatest at about the middle of each side, 

 where it is very little more than about one millimetre. 



Surface ornamented with coarse, gradually thickening ridges 

 radiating in all directions from the umbo, alternate ridges 

 slightly tiner than the others, and with interspaces nearly as 

 wide as the ridges. This ornament is crossed at distances of 

 about one millimetre, or slightly less, by strong and regular con- 

 centric ridges, giving rise to a coarse reticulation over the whole 

 surface. At the intersection of the radial and concentric ridging 

 it is slightly nodulose when worn, but most likely somewhat 

 squamose in the unworn condition. 



Dimensions. — Antero-posterior diameter, 40 mm. ; greatest 

 breadth, 2.5 mm. at about 9 mm. in front of the umbo ; height, 

 12 mm. ; sinus, 5 mm. broad by about 1 mm. deep. 



Localitv. — Eocene beds of Table Cape, Tasmania. One ex- 

 ample. 



Observations. — This is the flrst species of this genus described 

 from our Older Tertiary deposits, and it shows close relationship 

 with the living 7\s[alia parnwp/widea, Quoy and Gaimard, a not 

 uncommon shell from the coasts of Tasmania, Victoria and South 

 Australia. The present fossil species may however be distin- 

 guished from the living species, as it is of a different shape, being 

 more regularly oval and its greatest breadth being anterior to 

 the umbo ; whereas the living species is broadest across or 

 slightly posterior to the umbo, is proportionately broader and 

 more suddenly rounded at the anterior end, and when placed on 

 a flat surface the lateral margins are very much more highly and 

 distinctly elevated. Further, the fossil species is much more 

 coarsely ornamented and with coarser denticulations on the 

 margin. 



Ul. Entalis mantelli, Zittel. 



Dcntaliuni /iicksii, McCoy, Woods, itc, see R. Etheridge, jun., 

 Cat. Aust. Foss., p. 163. 



Dentaliiini mantelli, Zittel, Pal. von Neu-Seeland, p. 45, pi. 

 xiii., tig. 7, 1865. 



