RAPHITOMA COMPACTA. 385 



conditions of the Coralline- Waltonian period continued to be favourable, not only 

 to the existence of the present group of shells but generally to raolluscan life, 

 might have resulted in their becoming specifically distinct. The opening of 

 communication between the Crag basin and northern seas, shown by the sudden 

 appearance of so many boreal shells toward the end of the Waltonian epoch, 

 seems, however, to have brought about a different state of things resulting in the 

 gradual disappearance not only of R. mitrula and its congeners but of most of the 

 southern species of mollusca which up to that time had been abundant in Anglo- 

 Belgian seas. 



There is a box of 40 or 50 specimens, labelled Pleurotoma mitrula (Gr. 1898), in 

 the Wood Collection at the British Museum (Natural History) at South Kensington, 

 most of them agreeing with those figured by me on PI. XXIX, which Wood seems 

 to have regarded as the type form of the present species. 



Raphitoma compacta (Ktheridge and Bell). Plate XXXIX, fig. 7. 

 1898. Pleurotoma co»tj>acta, A. Bell, Trans. Roy. Geol. Soc. Cornwall, vol. xii, p. 138. 



Specific Characters. — Shell short, minute, fusiform, fairly strong and solid; 

 whorls 6, convex, subangulate, the last more than half the total length ; ornamented 

 by rather distant longitudinal costse reaching nearly to the base of the shell, and 

 crossed by fine and sharply-edged spiral ridges, causing slight tuberculation at the 

 points of contact ; suture deep ; mouth oblique, narrow, oval, angulate above, 

 passing into a well-defined and short canal ; outer lip slightly angulated by one of 

 the spiral ridges ; inner lip forming a thin glaze on the columella. 



Dimensions. — L. 5 mm. B. 2*5 mm. 



Distribution.— -Not known living. 

 Fossil : St. Erth. 



Renin vis. — This interesting little shell from St. Erth belongs to the Jermyn 

 Street Museum, and is figured by the kind permission of the Director of the 

 Geological Survey. Messrs. Etheridge and Bell, unable to identify it with 

 anything before described, recorded it under the above not inappropriate name. 

 Mr. Bell suggests it may be a young shell, but it is quite perfect and its dis- 

 tinguishing sculpture is clearly shown. 



Raphitoma substriolata, sp. nov. Plate XXXIX, figs. 14, 15. 



Specific Characters. — Shell small, strong and solid, smooth and polished, 

 elongato-subfusiform ; whorls convex ; without spiral sculpture but ornamented 

 by 8 or 9 strong, prominent, clearly-cut longitudinal costae which reach the base 



