CO^HGRYLIA—DITHYRA. 7. 29 



We cannot, as yet, agree with Lamarck and the French natural- 

 ists, that mere difference in shape or outline are always sutlicieut 

 grounds for strict specific character, circumstances often necessa- 

 rily occasioned by their confinement, and where the different com- 

 ponent parts of the rock they inhabit may be of more difficult so- 

 lution or decomjjosition. 



A competent knowledge of the rock shells seems at present by no 

 means to be fully attained or clearly understood : and we feel a con- 

 viction that much valuable information remains to be disclosed by 

 an attentive investigation and comparison of the inhabitants of 

 submarine masses. Our cabinet contains many curious anomalies 

 of whose determinate generic and specific fixture we are yet in 

 doubt, and which we have consequently forborne to record. 



Quartz, and the more compact kinds of granite, seem to resist 

 their action, as we have searched in vain for any traces of what are 

 deuominated borers, in Guernsey and the adjacent i.slands. 



Venekupis testa polymorphd, striis transversis anticS lamellatis long- perforans 



itudinalibusque minutis. 

 Shell variously shaped, with transverse striae which become lamel- 

 lar at the anterior end, and minute longitudinal ones. 



Tub. nost. 2, fig. 15 to 18. 

 Venus perforans. Montagu, Test. Brit. 127, tab. 3, fig. 6. 



Linn. Trans, viii. p. 89. 



Turton, Brit. Fauna, p. 159. 



Pennant, Brit. Zool. iv. p. 21 1. 



Dillwyn, Descript. Catal. p. 206. 



