236 MANUAL OP THE MOLLTJSCA. 



Operculum, Jiorny. 



Neverita, Risso. N. Alderi. Fig. 95. 



Lunatia, G-ray. N. Ampullaria. Perforation simple ; epider- 

 mis dull, oliyaceoTis. Northern seas. 



Olohulus, J. Sby. (Ampulina, Deshayes not Bl.) N. Sigaretina. 

 PL YIII., Fig. 2. Umbilicus narrow (rimate), lined by a thin 

 callus. 



Fossil, Eocene. Britain, Paris. 



Polinices, Montfort (naticella. Guild.), N. mammilla. Shell 

 oblong ; callus very large, filling the umbilicus. 



Cernina, Gray, N. fluctuata. PI. VIII., Fig. 3. Globular, 

 imperforate ; inner lip callous, covering part of the body- whorl. 



Naticella, Miiller. 19 species. 



Fossil, Trias, S. Cassian. 



Deshayesia, Eaulin 



Pliocene, France. Some additional species have been found 

 with a similar oblique aperture and corrugated inner lip. 

 Baron Eyckholt has described a species (D. Raulini), from the 

 Devonian, Belgium. The relation of the genus is uncertain. 



Naticella, Miinster. 



This genus, abounding in the Trias of St. Cassian, has been 

 referred to Natica by D'Orbigny. A characteristic species 

 occurs in the green-sand of Blackdown, and has been named 

 Natica carinata, J. Sby. (Narica, D'Orbigny.) It is exactly 

 intermediate between Narica (p. 237) and Fossarus (p. 253), and 

 appears to form with them a little group nearly related to 

 Lacuna (p. 255). 



SiGARETXis (Adans.), Lamarck. 



Synonyms, Cryptostoma, Bl. Stomatia, Browne. 



Type, S. haliotoides. PI. YIIL, Fig. 4. 



Shell striated ; ear-shaped ; spire minute : aperture very wide, 

 oblique (not pearly) ; operculum minute, horny, sub-spiral. 



The flat species are entirely concealed by the mantle when 

 living ; the convex shells only partially, and they have a 

 yellowish epidermis. The anterior foot lobe (mentum) is enor- 

 mously developed. 



Distrihufion, 31 species. West Indies, India, China, Peru. 



Fossil, 10 species. Eocene — . Britain, France, South America. 



Suh-genus. Naficina, Gray. N. papilla, PI. YIIL, Fig. 3. 

 Shell ventricose, thin, perforated. "West Indies, Eed Sea, China, 

 North Australia, Tasmania. Eocene, Paris. 



