24 SYSTEMATIC ARRANGEMENT 



** Foot very large, with a cross-groove on each side, often covering the 

 shell, and producing a polished coat on it (see p. 10). 



Fam. VII. OLIVID.E. 



Siphon of mantle recurved. Head small. Foot often enclosing a 

 part of the shell, with a cross groove on each side in front. Mantle 

 enclosed. Canal of shell reduced to a notch. Operculum horny, 

 small, annular, or none. 



a. Olivina. Shell suhcylindrical, smooth, polished; suture with a deep 

 channel; pillar plaited in front. Mantle with elongated pos- 

 terior process enclosed in the groove of the spire. Lateral 

 teeth broad, ovate. Operculum with subapical nucleus, or 

 wanting. 



1. Strephona. 



Shell suhcylindrical ; mouth linear. Frontal lohes small, acute. 

 Operculum none. 



1. S. sanguinolenta, t. 18. f. 1. 



2. S. textilina, t. 18. f. 2. 



3. S. elegans, t. 18. f. 3. 



4. S. erythrostoma, t. 18. f. 4. 



5. S. Maura, t. 18. f . 5 ; t. 102. f. 5. 



6. S. senegalensis, t. 83 a. f. 1. 



7. S. Ispidula, t. 101. f. 2, 3. 



8. S. , t. 100. f. 3. 



9. S. mauritiana, Adams, Gen. Moll. t. 15. f. 4. 



Foot of Strephona textilosa folded longitudinally. Lingual mem- 

 brane slender, transparent. Teeth 1 ■ 1 • 1 1 ; central transverse, very 

 short, three-toothed ; the lateral toothlet twice as large as central ; 

 lateral teeth triangular, rather curved at the tip, the outer rather the 

 largest. Operculum none. 



Tongue of Strephona Ispidula linear. Teeth 1-1*1; central 

 broad, three-toothed in front ; lateral small, lanceolate, ovate, acute, 

 slightly curved, variable. Operculum none. 



Teeth of Strephona cruenta 1 • 1 • 1 ; central three-toothed in front, 

 central denticle smallest ; lateral ovate ; when seen one over the 

 other, they appear narrower and subhamate. 



M. d'Orbigny described the aquiferous pores on the underside of 

 the foot, common to most marine Gasteropods, as a particular cha- 

 racter of the Olividce, observing that it is nearly unique among the 

 Gasteropods ! — Cuba, 104. 



2. Olivella. 

 Shell suhcylindrical ; mouth linear. Frontal lobes of animal small, 

 acute. Operculum distinct, half-ovate, rounded at each end, thin; 

 nucleus subapical, rather curved and within the edge. 

 1. O. volutella, Eydoux, t. 83 a. f. 2. 



