APPENDIX. 221 



NA HERCULEA, Rambur. PL 63, figs. 96, 97. 



Openly umbilicated, scarcely striulate ; whorls 5^. 



Diam. 19'5 mill. 



Monaco. 



Related to E. olivetorum ; and, so far, only found fossilized. 

 HYALINA LENTIFORMIS, Kobelt (unfigured). Minorca. 



Genus THYROPHORELLA, Greef., 1882. 



T. THOMENSIS, Greef. 



Shell sinistral, thin, transparent, nearly orbicular, with a 

 slight yellowish epidermis ; umbilicated ; whorls sharply keeled ; 

 aperture half-round, with a sharp simple margin, furnished with 

 a lid or extension of the upper portion of the peristome, which 

 is flexible, opening for the extrusion of the animal, closing the 

 aperture when it is withdrawn. 



Isl. St. Thomas, W. Coast of Africa. 



This curious and still unfigured mollusk has given rise to 

 much speculation among conchologists. The lid-like extension 

 has been regarded as analogous to a valve, making it a bivalve 

 terrestrial shell ; and the shell has also been supposed to be the 

 operculate larva case of some insect. Recent investigation has 

 shown it to be a true mollusk and to possess the dentition of the 

 Zonitidae 



