CONCHYLIA— DITHYi?^. 49. 221 



with pale rays : beaks separated by a linear transverse cavity : in- 

 side perlaceous, glossy except round the margin, which is extremely 

 thin : hinge with a single small tooth under the beak, which forms 

 a slight indentation in the opposite valve. 



49. Vm^A—LINNE. 



Testa longitudinalis cuneiformis aquivalvis, basi acuta rectiusculd, 



apice dilatato hiante. Cardo edentulus. Ligamentum externum, 



prcBlongum. 

 Shell longitudinal, wedge-shaped, equivalve, pointed and nearly 



straight at the base, dilated and open at the top. Hinge without 



teeth. Ligament external, and very long. 



These shells have a wedge-form or somewhat triangular shape, 

 and are fixed in gravelly and sandy parts of the ocean by the point- 

 ed end, near the termination of which issues a strong hair-like 

 byssus of attachment. 



Pinna testa ovato-trigond, striis transversis arcuatis, apice fastigiato, ingeus 



latere postico truncate recto. 

 Shell oval-triangular, with transverse arched striae, flat at top, 



truncate and straight at the hinder side. 



