CONCHYLIA—DITHYRA. 10. 37 



Mus. nost. Rocks in Torbay. 



Shell a quarter of an inch long, and half an inch broad, covered 

 with a brown wrinkled skin which extends beyond the anterior 

 end, wedge-form, truncate at the hinge, with the upper margin 

 often a little contracted about the niiddle, gradually tapering to 

 the auterior end which is slightly open; beaks rather prominent, 

 witli the points not quite opposite but divaricating from each 

 other: inside glossy white with a purplish tint, the margin sharp 

 and plain; the elevated tooth running in a gradually narrower 

 and wedge-shaped manner nearly half way along the back margin. 



Except for the very distinct and visible teeth, we should be 

 much inclined to think that this is the Mytilus praecisus of Montagn, 

 p. 165, tab 4, fig. 2. He speaks of his shell as not being uncom- 

 mon among rocks, subject to much variety of shape; and some 

 of our specimens much resemble his figure. 



Named from General Bingham, our diligent fellow-labourer 

 among the rocks in Torbay. 



Sphenia testa ovato-cuneatd, daite concavo horizontali-protenso. .Swainsoni. 



2 



Shell oval-wedge-form, with the concave tooth projectmg hori- ' 



zontally inwards. 



Tab. nost. 3. fig. 3, and tab. 19, fig, 2. 

 Mus. jiost. Rocks in Torbay. 



Shell about the size of the last: but is of a more oval form, 

 with tlie anterior end rounded, the beaks not so near the end, 

 and the concave tooth projects inwards like those of Anatina 

 pra^lenuis. 



