360 ' CALYPTRID^. 



Species of Crucihulum. 



auriculatum, Sow. radiatum, Brod. 



extinctorutn, Sow. rugosum, Desk. 



fastigiatum, Gould. spinosura, Soxv. 



hispidum, Brod. Tonganum, Quoy and Gaim. 



imbricatum, Brod. trigonale, Adams and Reeve. 



maculatum, Brod. umbrella, Desh. 



peziza, Gray. undulatum, Mart. 



pileolus, VOrb. Vanicorense, Quoy and 

 pileopsis, Quoy and Gaim. Gaim. 



Sub-gen. dispot^a, Say (Calypeopsis, Less). 

 Internal appendage entire, cup-shaped, laterally adherent, 

 cancellata, Adams and Reeve. striata, Say. 



Genus TROCHITA, Schumacher. 



Foot transversely oblong, bilobed at the middle in 

 front. 



Shell orbicular, trochiform, more or less spiral ; apex 

 central, whorls convex, radiately rugosely plicate, axis 

 imperforate ; aperture wide, with an oblique, transverse, 

 subspiral lamina, simple on the columellar margin. 



Sijn. ? Luna, Klein. Infundibulum, UOrh., not 

 Monif. Trochatella, Lesa., not Swains. 



Ex. T. occidentalis, Gray^ pi. 40, fig. 5. Shell, T. 

 radians, Lamarck, fig. 5, a. 



The apex of the cone in this genus assumes a more or 

 less spiral form, and the internal lamina of the aperture 

 is partly twisted, and partakes of the character of a rudi- 



