DESCRIPTION. 135 



sides plaited, denticulate; lower valve smooth, 

 channelled in the middle, upper one rough with 

 elevated points upon the margin, and an elevated 

 central rib. 



Inhabits the American Ocean. 



Fig. 5. M. margaritiferus. 



Shell compressed, flat, suborbicular ; hinge 

 transverse, imbricate, having the laminae toothed 

 in rays. 



Lister Conch. Tab. 223. Fig. 57. 



Specimen whitish with crimson rays, within 

 pearly ; being young, it does not possess the tooth- 

 like scales which are found in older shells. Hinge 

 very straight, the length of the whole shell. 



Inhabits the American Ocean. 



A distinct variety, differing in size and in other 

 respects from the East Indian Pearl-bearing muscle. 



Fig. 6. M. edulis. 



Shell smooth, violet ; valves rather carinate 

 before, retuse behind, beaks pointed . 

 Lister Conch. Tab. 362. Fig. 200. 



