CEEITHIUM. 225 



in adults is ovate ; the callosity of the posterior canal is deeply 

 channelled, outer margin smooth, slightly callous, and spread 

 outwardly ; inner margin concave, callous, and columella twisted ; 

 anterior canal short, bent at an angle of about 45° from the 

 axial line. 



The figure accompanying Tenison- Woods' memoir above quoted 

 refers to a mere fragment, and it seems advisable to refigure the 

 shell (see Plate VII. Figs. 1, 2). 



Dimensions. — Length 103 mm.; breadth 22 mm.; length of 

 aperture 18 mm. 



Form, and Loc. — Eocene : Muddy Creek, Victoria. 



G. 4154. Two examples of the adult. 



Presented by John Dennant, Esq. 



G. 5534. Several examples of a variation in which the 

 longitudinal costsB are more pronounced, and extend from the 

 earlier whorls to the body-whorl in the adult ; the costse are 

 closer together, and the granulated threads accompanying the 

 suture are bolder than in typical examples, whilst the shell is 

 relatively broader. Purchased. 



Cerithium pritcliardi, nom. mut. 



[Plate VII. Fig. 3.] 



1885. Fofamidfs semicostafum, Tate, Pap. Eoy. See. Tas. 1884, p. 226 {non 



Deshayes) . 

 1896. rotamides semicostafum, Piitcliard, Proc. Koy. Soc. Vict. vol. viii. 



N.s. p. 116. 



Shell large, solid ; composed of about twelve flattened whorls ; 

 much widened towards the anterior aspect; suture undulating, 

 slightly incised; ornament of the whorls consisting of immense 

 distant, elevated, rather oblique, obtuse costse extending over 

 the anterior half of the whorls only, 10-11 in number on the 

 penultimate whorl, the whole surface of the whorls covered by 

 close, irregular, spiral striations, interrupted by the slight corruga- 

 tions of growth ; suture in the adult bordered anteriorly by more 

 or less obsolete tubercles ; ornament of the last whorl abruptly 

 ended by a large variciform ridge ; inner margin of the aperture 

 callous, carrying a prominent ridge posteriorly ; columella 

 excavated. 



Q 



