CONCHYLIA— D/THYR^. xxxiii. 



33. Crassina. 



* margine interno integerrimo. 

 with the inner margin very entire. 



1, subrhomboidea, anticS truncata, transversim rugosa. 



truncate at the anterior side, and wrinkled 

 transversely. 



2. Scotica, orbicularis, costis transversis rotundatis. 



orbicular, with rounded transverse ribs. 



** margine interno denticulato. 

 with the inner margin toothed. 



S. sulcata, orbicularis, costis transversis rotundatis. 



orbicular, with rounded transverse ribs. 



34. Myrtea. 

 I. spinifera, Myrtea. 



35. Cyprina. 



1. Islandica. area ohsoletd, dentibus tribus cum laterali remoto. 



the area obscure, with three teeth and a remote 

 lateral one. 



2. compressa, transversim costata, dentibus duobus cum laterali. 



transversely ribbed, with two teeth and a lateral 

 one. 



3. triangularis, loevis, valvd altera tridentatd. 



smooth, with three teeth in one valve. 

 •D 



