PHOLADIS. Lam. Turt. B. p. 20. t. 2. /. 10. 

 MYTILUS R; Lin. 1156. Pew. 4. p. 110. t. 63./. 72. 

 D.|>.304. Mont. p. 164. Dor. Ca*.^. 39. *. 13. 

 /. 6. Turt. D. p. 1 13. Lin. T. S.p. 270. *. 6./.3, 

 4. ii*. . 426. /. 267. Rounded posteriorly, sub- 

 truncated anteriorly, the ventral edge slightly incurved 

 near the middle, dull white under a greyish wrinkled 

 cuticle, coarsely wrinkled transversely. i...l. Common, 

 in Rocks. 



H. ARCTICA. Lam. F. p. 461. H. MINUTA. and 

 OBLONA. Turt. B. p. 24. t. 2. /. 12, 3. SOLEN Mi- 

 NUTUS. Lin. \\\5.Mont.'p. 53. t. I./. 4. Ch. f. 

 51^ 2. Wood. G. C. p. 139. t. 34. / 5, 6.!).^. 

 69. Turt. C. D.p. 161. With two diverging spinous 

 ridges on the anterior slope; closel} resembling the 

 former specie in age by the gradual disappearance of 

 the spinous ridges, but distinguished by the greater 

 incurvation of the ligame.ital edge. The Mytilus 

 Prcecisus of Mont. p. 165. t. 4. /. 2. seems but a 

 variety of this species. 



GENUS. AGINA. TURTON. 



Transverse, oval, equivalve, inequilateral, open at the 

 anterior end ; hinge with a single erect conic per- 



