XX* CONCHYLIA—JDITHYRA. 



Character specificus essentialis. 

 Essential specific character. 



A. TESrm MARIN M. 1—52. 



SEA SHELLS, 



1. Pholas. 



* valvis sulco longitudinali divisis. 



the valves divided by a longitudinal groove. 



J. papyracea, anniilo prodacto postico. 



with a produced ring- at the hinder end. 



2. lamellata, lamella erectci supra denies. 



with an erect lamina above the teeth. 



3. tuberculata, tuherado scabro supra denies. 



with a rough tubercle above the teeth. 



4. crispata, margine supra datites mnlico. 



with the margin above the teeth smooth. 



** valvis medio indivisis. 

 the valves undivided in the middle. 



5. Dactylus, margine postico celluloso. 



cellular at the hinder margin. 



