226 CEEITHIUM. 



The circumstance that the aperture is not perfect in the 

 specimens described by Professor Tate has, naturally, rendered it 

 difficult to state the generic position of this species. The 

 specimens in the Museum collection are not perfect in that respect, 

 but the present writer assigns the species to Cerithium rather than 

 to Potamides on account of its close resemblance to G. semicostatum, 

 Deshayes, of the Lower Eocene of North-West Europe. It is 

 always difficult to discriminate between the two genera mentioned 

 in the fossil state, but, typically, Cerithium is a marine organism, 

 whilst Potamides inhabits brackish and fresh waters. The beds at 

 Table Cape are certainly of marine origin, and that lends support 

 to the view that the present species is a Cerithium. As before men- 

 tioned, however, the circumstance that C. semicostatum, Deshayes, 

 of the European Eocene is undoubtedly a Cerithium * (of the 

 subgenus Vulgocerithium '), is one of the chief reasons for the 

 present classification of the Tasmanian form. 



On being assigned to Cerithium, the specific name proposed by 

 Professor Tate is preoccupied by C. semicostatum, Deshayes; the 

 species is now named in honour of Mr. G. B. Pritchard, a well- 

 known worker on the Table Cape beds. 



Dimensions (of an imperfect specimen). — Length 75 mm.; 

 breadth 24 mm. 



Form, and Loc. — Eocene : Table Cape, Tasmania. 



G. 9491. Two examples. Purchased. 



Cerithium flemingtonense, M'Coy. 



1876. Cerithium Jlemingtonensis, M'Coy, Prod. Pal. Vict. dec. iii. p. 28, 



pi. xxvi. figs. 3-9. 

 1878. Cerithium Jlemingtonensis, E. Etheridge, jun.. Cat. Aust. Foss. p. 160. 



Form, and Loc. — Lower Pliocene : Elemington, north of 

 Melbourne, Victoria. 



G. 9688. Cast of the adult in hard ferruginous sandstone ; too 

 imperfect for description. 



Transferred from the Museum of Practical Geology. 



^ See Cossraann, Ann. Soc. Roy. Malac. Belg. t. xxiv. 1889, p. 16. 

 ^ Id. t. xxxi. 1896 (separate copy), p. 28. 



