102 MYA. GAPER. 



lar tooth in each valve, hollow in the middle, and project- 

 ing inwards horizontally : length three-quarters of an inch; 

 breadth an inch. 



It differs from Mya praetenuis, in having the margin al- 

 ways irregularly waved. 



Burrowed in limestone, v. v. 



9. Mya bidentata. Double-toothed Gaper. 

 Montagu, pi. 26. f. 5. 



Shell thin, flattish, somewhat oval, quite smooth, white 

 but not glossy, often covered with a roughish extraneous 

 coat, smooth within : hinge with two broad erect laminar 

 teeth in one valve, which diverge outwards from each other, 

 and are not very close together, with a slight cavity between 

 them ; in the other valve no teeth : length the eighth of 

 an inch ; breadth rather more. 



Imbedded in the convex valves of old thick oyster-shelly 

 just beneath the surface, v. v. 



10. Mya decussata. Decussate Gaper. 

 Montagu, pi. 28. f. 1 . 



Shell oval, white, waved at the margin, with irregular 

 concentric ridges, crossed by regular longitudinal striae, 

 which form tubercles at the anterior end ; inside smooth, 

 white : beaks obtuse, recurved, placed near. * to one end : 

 hinge with a broad erect tooth in one valve ; in the other a 

 projecting plate, with a small indentation: length nearly 

 half an inch ; breadth rather more. 



In the Firth of Forth : rare. 



11. Myapurpurea. Purple Gaper. 



Montagu, Suppl. p. 21. 



Shell oval, whitish, growing purple towards the beaks, 

 slightly wrinkled transversely.; inside paler, with a plain 

 margin : beaks placed considerably on one side, and turn- 

 ing towards the shorter end : hinge with a slightly notched 

 erect tooth in each valve : length hardly a line j breadth 

 rather more. 



Devon coast, among Corallines : rare. p. v. 



12. Mya ferruginosa. Rusty Qapcr. 

 Montagu, pl f 26. f. 2. 



Shell 



