30 



One fifth of the margin of our shell shows the diagonal 

 strise, nearer approaching those of the common circles re- 

 ceding from the hinge. T, Fahula continues the same 

 throughout. Both shells are diagonally striated in ours, 

 and only one shell in T. Falmla; the other being remark- 

 ably smooth and polished, with but few of the common 

 concentric striae. Our shell is rather yellower. Both 

 require a magnifier to see the striae distinctly, and then 

 often show prismatic hues of a pearly nature. 



