CONCHYLIA— D/THYil^. xxi. 



6. parva, tuberculo IcBvi supra denies. 



with a smooth tubercle above the teeth. 



7. Candida, denticulo curvo supra dentem. 



with a curved denticle above the tooth. 



8. striata, lamina, planatd recurvd externa. 



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 obliquo supra denies. 



with an oblique conic denticle above the teeth. 



2. bipennata, casta obliqud supra denies. 



with an oblique rib above the teeth. 



3. dorsalis, costd longitudinali interna. 



with a longitudinal rib on the insida 



3. Gastroch^na. 



1. pholadia, loevis umhonibus subierminalibus. 



smooth, with the beaks nearly terminal. 



4. Saxicava. 



1. rugosa, antic^ subangulata truncata. 



somewhat angular and truncate at the anterior end. 



2. Pholadis, extremitatibus rotundatis. 



rounded at both the sides. 



