OLIVELIA. Yl 



tricuspidate; on the other hand, a typical OUvella has neither 

 tentacles nor eyes, ami the median tooth of the radula carries a 

 great number of small denticles, in addition to which the radula 

 has accessory lateral plates. In spite of these important anatomical 

 differences, the shells of certain species of both genera closely 

 resemble each other, and it is, therefore, almost impossible to 

 classify them with any degree of accuracy from an examination 

 of the test alone. Fortunately, however, the more extreme forms 

 of the shells are not difficult to determine generically, and the 

 Australasian Tertiary fossils about to be described are allocated 

 to the genus OUvella without much doubt. 



In general, the shells may externally be distinguished from 

 those of OUva by the columella not being plicate (or lirate) 

 throughout its entire length, whilst the columellar border is more 

 obliquely inclined with reference to the axis, and is sometimes 

 slightly excavated (as in 0. nymphalis, Tate) ; the spire is more 

 elevated, though this last character is by no means constant. 



Ti/pe.— Oliva Uplicata, G. B. Sowerby. 



Olivella angustata, Tate (sp.). 



1889. OUva angmtata, Tate, Trans. Roy. Soc. South Aust. vol. xi. p. 144, 



pi. \m. figs. 7a-*. 

 1889. OUva angustata, Dennant, id. vol. si. p. 43. 



The spire in this species is long, in adult specimens being more 

 than one-third the entire length of the shell ; suture deep ; aper- 

 ture narrow, wider where the columella is slightly excavated; 

 plications variable in number, situated on the anterior half of the' 

 columellar border only. 



Compared with 0. nitidula, Desh., of the Parisian Eocene, it is 

 found to be longer, its aperture is narrower and straighter, and 

 Its columella is less excavated ; in other respects it presents con- 

 siderable analogy with the shell of that species. 



Dimensions. — Length 26 mm.; breadth 8-5 mm. ; length of 

 aperture 15-5 mm. 



Form, and Zoc— Eocene : ]\:uddy Creek, Victoria. 



G. 4170. Three specimens. Presented hy John Dennant, Esq. 



G. 9367. Examples showing stages of growth. Purchased. 



