ESSENTIAL GENERIC CHARACTERS. XXVll 



a little angular or rounded, and contracted transversely : pillar 

 placed obliquely. 



26. TURBO. Shell spiral, solid : aperture contracted, entire, 

 more or less orbicular. 



27. HELIX Shell spiral, more or less transparent and brittle : 

 aperture contracted, roundish or crescent-shaped. 



28. NERITA. Shell spiral, gibbous, flattish underneath : 

 aperture half orbicular; the pillar-lip transverse, flattish and 

 truncate. 



29. HALIOTIS. Shell ear- shaped, almost entirely open, with 

 a longitudinal row of orifices towards the outer margin : spire 

 lateral, flat upon the back. 



2. Without spire. 



30. PATELLA. Shell shaped like a bason, more or less conic, 

 generally without spire. 



31. DENTALIUM. Shell linear, tubular, not divided into 

 chambers, open at one or both ends. 



32.SERPULA. Shell tubular, variously shaped, sometimes se- 

 parated by internal divisions at irregular distances, 



ENGLISH 



