(64) 



ORDER V. PEGTINIBRANCHI. 

 FAMILIES. 



1. Trochoida. 



Shell spiral, mouth en- An operculum, 

 tire, without notch or ca- 

 nal. PI. 9, fig. 7. 



2. BUCCINOIDA. 



Shell spiral, with a 

 notch or canal for the 

 passage of the siphon, 

 which is a prolonged fold 

 of the mantle. PI. 10, fig. 

 21. 



3. SlGARETOlDA. 



Shell flattened, hidden 

 during life within a spon- 

 gy buckler which is the 

 true mantle. PI. 5, fig. 25. 

 PI. 14, fig. 15, 16. 



