:. CO'i^CEYLlA—DITHYRA. 



Character speciflcus essentialis, 

 Essential specific cliaracter. 



A. TESTjE MARINJE. 1—52. 



SEA SHELLS. 



1. Pholas. 



* 



valvis sulco longitudinali divisis. 



the valves divided by a longitudinal groove. 



1. papyracea, annulo producto, postico. 



with a produced ring at the hinder end. 



2. lamellata, lamella erectd supra denies. 



with an erect lamina above the teeth. 



3. tuberculata, tuherculo scabro supra denies. 



with a rough tubercle above the teeth. 



4. crispata, margine supra denies mutico. 



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. 



