' 49 



Iongitiidinal7?77Ve; ?^w6o placed near to one end ; beakfmall, 

 turning towards the fhorter fide. Infide moderately con- 

 cave and fmooth ; margin plain : hinge furnidied with three 

 teeth, that next to the cartilage is long and oblique, forming 

 a cavity between it and the margin for the reception of the 

 cartilage ; the two other teeth are fliort, the middle one is 

 the longeft. Length half an inch ; breadth fomewhat more. 



Rare : three fingle valves only were taken in the dredge 

 off the Ijle of May\ Frith of Forth, by the fame gentleman 

 as took the laft. 



Shell fub-rhomboidal, rounded at one end, truncated at Subrhomboidea. 

 the other, and irregularly wrinkled concentrically, efpecially Tab, 28, f.2. 

 towards the margin, where the ridges are prominent, but 

 obtufe ; tliefe are decuflated by extremely fine approxi- 

 mate longitudinal7?r/V? : umbo fmall and nearly central, but the 

 beak reclines to one fide : the colour is white with a tinge of 

 ^ufous at the truncated end. The infide is white with a dafli of 

 purple at that part whicli is rufous on the outfide ; the mar- 

 gin is plain : cicatrix broad, fpreading half acrofs the fhell : 

 the hinge is fingularly formed ; in each valve are two firong, 

 plain teeth, one of which fiands very oblique ; behind thefe 

 the margin proje6ls inwards, and then doubling back forms 

 a fmooth replication, and a cavity between it and the exterior 

 edge of the fhell behind the umbo, for the connecting car- 

 tilage. Length half an inch ; breadth three quarters. 



G For 



