CONCHYLIA— DITifYi?^. 



Character genericus essentialis, 

 Essential generic cliaracter. 



A. 



Ligamentum nullum. 

 Liaameut none. 



1. Pholas. — Testa transversa, ovata. 



Shell transverse, oval. 



2. Teredo. — Testa orbicularis, hemisphcErica . 



Shell orbicular, hemispherical. 



B. 



Ligamentum externum. 

 Ligament external. 



* Cardo edentulus. 



Hinge without teeth. 

 4. Saxicava. — Testa transversa, latere antico hiante. 



Shell transverse, open at the anterior end. 

 53. Anodon. — Testa transversa, sinu marginali antico. 



Shell transverse, with a marginal depression on 

 the anterior side. 

 •2 A 



