COI^CEYLIA—DITHYRA. xx> 



28. LuciNA. 



* fovea interna obliqud. 



with the internal cavity oblique. 



1. lactea, orbicularis, striis transversis irregularibus. 



orbicular, with irregular transverse striae. 



2. Leucoma, subobliqua subjlexuosa, striis crebris regularibus. 



somewhat oblique and flexuous, with crowded 



regular striae. 



** fovea interna rectiusculd. 



with the internal cavity nearly straight. 



3. alba, valvd altera unidentatd. 



a single tooth in one valve. 



4. rotundata, valvis bidentatis, loevis. 



the valves two toothed, smooth. 



6. Radula, valvis bidentatis, striis crebris laminatis. 



the valves two-toothed, with crowded laminar 

 striae. 



5. undata, valvd altera tridentatd. 



one of the valves with three teeth. 



29. Strigilla. 



J . carnaria, striis hinc flexuoso-angulosis. 



with the striae angularly flexuous on one side. 

 2. pisiformis, striis hinc acutangulosis. 



the striae acutangular on one side. 



