COlSiCHYLlA—niTIfYR^. h 



\, TROLAS—LINNE. 



Testa transversa, ovata, cequivalvis, ineequilateralis, hinc Mans, 

 accessories difformibus scepius instructa. Cardo dente longo curvo 

 sub marginem inserto, in utrdque valvd : lateralibus nullis. Liga- 

 mentum nullum. 



Shell transverse, oval, equivalve, inequilateral, open at one or both 

 the sides, and often furnished with differently shaped accessorial 

 valves. Hinge with a long curved tooth in each valve, inserted 

 under the margin : lateral teeth none. Ligament none. 



J. HIS genus, and that of the Teredo, are remarkable in being 

 destitute of permanent ligament to connect the two valves ,• a sup- 

 port which their natural and constant lodgement in stone and wood, 

 seems to render less necessary than to the free bivalves, which are 

 exposed to external agitation and accidents. 



B 



