ASTRALIIN^. 397 



the peritreme ; inner lip moderate, with a thickened 

 callosity. 



E.V. C. marginata, Nuttall, pi. 44, fig. 2. Operculum. 

 C. marginata, fig. 2, a, 2, b. 



This genus comprehends several species of small turbo- 

 like shells, mostly African ; the fossil species of the Paris 

 Eocine are larger and tolerably numerous; the genus is 

 peculiar in the operculum and in the contraction of the 

 aperture at the peritreme. 



Species of Collonia. 



brevis, i>'(9/-i. (Phasianella). " phasianella, C. B. Adams. 



cingulata,P/u^. (Delphinula). pyropus, Reeve. 



coralliua, Reeve. rubrocincta, Migh. 



granulata, Bkr. (Delphinula). sanguiuea, Linn. 



marginata, Nutt. verruca, Gould. 



murrea, Reeve. violacea, Gould. 

 neritina, Dkr. 



Sub-fam. ASTRALIIN^. 



Operculum oblong or ovate, with an external, solid, 

 calcareous coat. 



Shell solid, trochiform, flat or concave at the base, 

 whorls rugose or spinose, the last often stellate or 

 keeled ; aperture usually sub-quadrate. 



Genus ASTRALIUM, Link. 



Operculum ovate, flat, rather thinner at the edge, with 

 a sub-central tubercle over the axis, and abroad, sub-mar- 

 ginal, spiral rib. 



