396 TURBININifl. 



is characterised by an extreme beauty and complexity of 

 structure. 



Sijecies of Callopoma. 



fluctuatum, Gray. tessellatum, Kien. 



saxosum, Wood. 



Genus NINELLA, Gray. 



Operculum concave externally, with two marginal, 

 raised, spiral ribs, and a thin edge. 



Shell turbinate, depressed, rugose, axis widely umbili- 

 cated, umbilicus perspective; aperture circular; inner 

 lip broad, excavated, with a pearly, spoon-shaped pit near 

 the columella, and a deep, longitudinal groove externally. 



Ex. N. staminea, Martyn, pi. 44, fig. 1. Operculum, 

 N. staminea, fig. 1, rt, 1, 6. Shell, N. staminea, fig. 1, c. 



There are two species at present known of this curious 

 genus, which seems to be intermediate between AstraUum 

 and Turbo; the form of the aperture and operculum, 

 however, would refer it to this division. 



Sjjecies of JSinella. 

 lamellosa, Brod. staminea, Mart. 



Genus COLLONIA, Gray. 



Operculum circular, with many gradually-enlarging 

 whorls, a convex external rib, and a central pit. 



Shell small, solid, turbinate, smooth, transversely 

 striated, axis imperforate ; aperture circular, contracted at 



