C01SCHYLIA--DJTHYRA. xxl 



6. parva, tuherado Icevi supra denies. 



with a smooth tubercle above the teeth. 



7. Candida, denticulo curvo supra dentem. 



with a curved denticle above the tooth. 



8. striata, laniind planatd recurvd externd. 



with a flat recurved external lamina. 



2. Teredo. 



1. navalis, denticulo curvo supra dentem. 



with a curved denticle above the tooth. 



4. nana, denticulo conico ohliquo supra denies. 



with an oblique conic denticle above the teeth. 



2. bipennata, costd ohliqud supra denies. 



with an oblique rib above the teeth. 



3. dorsalis, cosld longiludinali inlernd. 



with a longitudinal rib on the inside. 



3. GASTROCHiENA. 



1. pholadia, Icevis, umbonibus subterminnlibus. 



smooth, with the beaks nearly terminal. 



4. Saxicava. 



1. rugosa, anticb subano-ulata truncata. 



somewhat angular and truncate at the anterior end. 



2. Pholadis, exlremitatibus rotundatis. 



rounded at both the sides. 



