Gasteropodous Mollusca into larger Groups and Families. 127 



c. Purpurina. Operculum oblong ; nucleus elongate, forming 

 the long outer edge. Purpura, Concholepas, Sistrum, "tMagillus. 



It is to be observed that tbe operculum of tliese two families 

 offers exactly the same modifications. 



Planaxina, which have been arranged in this family, have a 

 distinct rostrum and operculum like Littorina. 



Fam. 3. Olivid.«. Siphon of mantle recurved ; foot with a 

 cross groove on each side in front ; often enclosing part of the 

 shell ; mantle enclosed ; operculum small or none. 



a. Olivina. Pillar of shell plaited in front. 



* Lateral teeth broad ovate. Strephona, Olivella, Scaphula, 

 Agaronia. 



** Lateral teeth hook-like, nan-ow. Ancilla. 



? b. Harpina. Pillar of shell smooth. Harpa. Teeth ? 



Pam. 4. LAMELLARIAD.E. Lateral teeth simple, curved; man- 

 tle very large, covering the shell, with a notch in place of the 

 siphon in front ; operculum none. Lamellaria, Coriocella. The 

 genus Marsenina [prodita) appears more alhed to Velutinida. 



B. Odontoglossa. Teeth on lingual membrane in three series 

 (1 • 1 • 1), the central recurved, toothed at the tip, the lateral not 

 versatile (figs. 2, 3). 



Pam. 5. Pasciolariad.^. Mantle enclosed ; siphon and canal 

 of shell straight ; shell with plaits on the front of the pillar ; 

 central tooth narrow, small ; lateral teeth very broad, linear, with 

 many equal teeth (fig. 2). Fasciolaria, Lagena. 



Pam. 6. TuRBiNELLiD^. Mantle enclosed ; siphon and canal 

 of shell straight ; shell with plaits on the middle of the pillar ; 

 central teeth broad, few-toothed ; lateral teeth narrowed, strong, 

 with a single large tooth (fig. 3). Turbinellus, Cynodonta. 



C. Rachiglossa. Teeth on lingual membrane in a single central 

 series, often toothed (figs. 4, 5). 



Pam. 7. VoLUTiDiE. Shell with plaits on columella ; siphon 

 recurved, and canal very short. 



a. Volutina. Siphon with auricles on side of base ; tentacles 

 far apart, united by a broad veil over the head. 



* Teeth lunate, apex 3-toothed (fig. 4). Yetus, Cymbium, ?Vo- 



luta. . 



** Teeth linear, base angularly diverging, with a single conical 



apex (fig. 5). Cymbiola. 



