526 PLIOCENE MOLLUSCA. 



Dimensions. — L. 7 mm. B. 2*5 mm. 



Distribution. — Recent : Madeira, Porto Santo, Selvagens, Grand Canary. 

 Fossil : St. Erth. 



Femarls. — I am indebted to my good friend M. Dautzenberg for identifying 

 the charming St. Erth fossil from the British Museum here figured (which there 

 bears the name of Cerithiuni tuberculatum, no. 18156), with a specimen of Bittlnm 

 incile he received in 1898 from Canon Norman. The Rev. R. Boog Watson, who 

 first described this species, states tliat it is very common in the waters of the 

 Madeira Sea. Our shell is quite fresh and perfect, and does not seem to have 

 been carried far from its original home. The occurrence of this and other 

 distinctly southern species in the St. Erth bed is not only interesting but 

 suggestive. Two other fossil species of Bittium are also known from that locality 

 which are unrecorded as living forms. 



Bittium dissimile, sp. nov. Plate XLVII, fig. 5. 



1898. Cerifhium reticidaium, var. inmduluin (not C. variculosum, Nyst), A. Bell, Trans. Roy. Geol. 

 Soo. Cornwall, vol. xii, p. 144, pi. i, fig. 12. 



Specific Characters. — Shell small, turreted, fairly solid ; whorls 9 or 10, slightly 

 convex ; ornamented by about 10 rounded and rather prominent longitudinal costae 

 intersected by spiral ridges, 4 on each wdiorl, which become granulate at the point 

 of contact; spire forming an elongated cone, regularly diminishing in size to a 

 blunt point ; mouth small, subovate. 



Dimensions. — L. 5 mm. B. 2 mm. 



Distribution. — Not known living. 

 Fossil: St. Erth. 



Remarks. — The St. Erth fossil, here figured as a new species, is also from the 

 Warburton Collection, where it is labelled " Gerithium punctulum " — a name given by 

 Wood in 1842 to a shell from Walton,^ which was afterwards identified by him, 

 but I think in error, with an Oligocene species, the G. variculosum of Nyst.^ In 

 Vol. I, p. 418, PI. XLI, fig. 5, I described and refigured Wood's Walton shell, 

 which is still in the British Museum under its original specific name of 

 punctuluniy reporting it also from St. Erth on the strength of Mr. Bell's identi- 

 fication given above. Comparing the two specimens and the two figures from 

 Walton and St. Erth respectively, however, I find they are not the same ; I 

 therefore describe the latter as a new species, B. dissimile, with which view 

 MM. Dollfus and Dautzenberg concur. 



1 Ann. Mag. Nat. Hist. [1], vol. ix, p. 538, 1842. 

 ~ Mon. Crag Moll., pt. i, p. 69, pi. viii, fig. 3, 1848. 



