SOLARIUM. 



deciduous or must in general have been carefully cleared 

 off before the shell is brought to England, for it is scarcely 

 ever to be seen. The operculum which is horny, varies 

 in form, according nearly in shape with the aperture; it 

 is foiiaceous and more or less distinctly spiral ; in one 

 species its foliated edge forms an elevated spiral cone on 

 the outer side ; this outer side is, however, flat in the 

 common species ; the inner side in both species has an 

 irregular, somewhat lateral tubercle. 



Solarium appears to be most nearly related to Tro- 

 chus; its recent species are not numerous, but they seem 

 mostly to belong to tropical climates: a few fossil species 

 occur in the tertiary beds; and there are some fossils be- 

 longing to the lower beds of oolitic formation, and even 

 as low as the Mountain Limestone which resemble them 

 very nearly; these form the genus Cirrus of some authors, 

 and does not appear to us to possess any characters by 

 which it may be generically distinguished from the Trochi^ 

 Turbines or Solaria. 



We have given two views of Solarium perspectivum, 

 and of its operculum; and also a representation of the 

 small spiral operculum of S. variegatum. 



