PLATE VI 



TOPOGRAPHY OF GASTROPOD SHELLS 

 i. Bursa lampas, Lamk. 



2. Septa tritonis, Linn.: a., apex; a.c, anterior canal; b.w., body 

 whorl ; c, columella ; c, inner, columella lip, or labium ; m., mouth ; 

 o.I. , outer lip, or labrum ; ^..periphery; p.c, posterior canal; s. suture ; 

 sm., septum ; sp., spire ; v., varix ; w., whorl. 



3. A series of sections of Natica, showing the successive infilling of 

 the umbilicus (11.) by callus (c): A, Natica heros, Say; B, N.didyma, 

 Bolt. ; C and D. N.Recluziana, Desh. ; E, N.mamilla, Linn. 



exhibition in the Natural History Museum. 



