stress has been laid, is too variable, as we Eave ju&lseew 

 in the g-enus Corbula at tab. 362, to be relied upon ; and 

 an examination of the recent species is still wanting t® 

 establish the two other points : the erosion of the ura- 

 bones does not occur in the other fossil species. 



First observed by Mr. Webster (Trans. Soe. GeoI.VIl, 

 p. 227), and ag-ain by Mr. G. B. Sowerby, who has com- 

 pared it to Mya labiata (Annals of Phil, new series. Vol. 

 II. p. 220). They fonnd it near the top of Headon Hill : 

 Prof. Sedgwick has since found it at Calbourne ; and it 

 probably occurs near the top of the upper fresh-water 

 formation on other parts of the Isle of Wight» 



MYA arenaria. 



TAB. CCCLXIV. 



Spec. Char, Ovate, auterioFly ratlier poinieflj 

 posteriorly rounded ; hinge tooth large^ 

 with a lateral appendage. 

 Mya arenaria. JLimi. et Aiictorimi. 



feo perfectly does this resemble the recent Mya arenaria,, 

 that we can find no distinguishing mark. In all proba- 

 bility this is one of the few shells belonging to genuine 

 diluvian deposits, and accidentally mixed with the older 

 fossils. It is frequently found, but rarely perfect, in the 

 Crag pits of Norfolk and Suffolk. I first received it 

 from Mrs. Cobbold of Ipswich. The figures are takeu 

 from specimens in the possession of the Rev. G. R. 

 Leathes, 



