CO^QT^YMJL—JDTTirTR^. 1. 



1. vnOhk^—LINNE. 



Testa transversa, ovata, aquivalvis, incequUateralis, hinc hians, 

 aecessoriis difformibus sfBpius instructa. Cardo dente Ipngo 

 curvo sub marginem inserto, in ntrdque valpd : laieralibus 

 nuUis. Ligamentum nullum. 



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

 both the »ides, and often furnished with diiferently shaped 

 accessorial valves. Hinge with a long curved tooth in each 

 valve, inserted under the margin : lateral teeth none. Liga- 

 ment none. 



JTHIS genus, and that of th« Teredo, are remarkable in being 

 destitute of permanent ligament to connect the two valves • a 

 support 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. 



