12-1; MANUAL OF THE MOLLUSCA. 



SiGAKETUS (Aclans.), Lamarck. 



St/n., crrptostoma, Bl. Stomatia, Brovme. 

 Ti/pe, S. haliotoides. PI. YIII., 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 ante- 

 rior foot lobe {mentimi) is enormously developed. 



Distr., 26 sp. "W. Indies, India, China, Peru. 



Fossil, 10 sp. Eocene — . Brit., France, S, America. 



Suh-genv.s, naticina. Gray. N. papilla, pi. YIII., fig. 3. SheU ventricose, 

 thin, perforated. W. Indies, fied Sea, China, N. Austi-alia, Tasmania. 

 Eocene, Paris. 



Lamellaria, Montagu. 



Eti/m., lamella, a thin plate. 



Si/n., marsenia, Leach. Coriocella, Bl. 



Ti/pe, L. perspicua. PI. YIII., fig. 6. 



Shell ear-shaped ; thin, peUucid, fragile ; spire very small ; aperture 

 large, patulous ; inner lip receding. No operc. 



Animal much larger than the shell, which is entirely concealed by the 

 reflected margins of the mantle ; mantle non-retractile, notched in front ; eyes 

 at the outer bases of the tentacles. Lingual tincini 3, similar ; or one very 

 large. 



Distr., 5 sp. Norway, Brit., ^Sledit., New Zealand, Philippines. 



Fossil, 2 sp. Miocene — . Brit. (Crag.) 

 Naeica, Eecluz. 



Si/n., vanicoro, Quoy. Merria, Gray. Leucotis, Sw. 



Ti/pe, N. canceUata.* PI. YIII., fig.'s. 



Shell thin, white, with a velvety epidermis ; ribbed in-egularly, and spi- 

 rally striated ; axis perforated. Operc. very small, thin. 



Animal, eyes at the outer base of the tentacles; foot with wing-like lobes. 



Distr., 6 sp. W. Indies, Nicobar, Yanikoro, Pacific. 



Fossil, 4 sp, Gault — (D'Orb.) Brit., France. 

 Yelutina, Fleming. 



Ftym., vehdinus, velvety (from veil us, a fleece). 



Type, Y. Ifevigata. PI.' YIII., fig. 7- 



Shell thin ; -^-ith a velvety epidermis ; spire smaU ; suture deep ; apertm-e 

 veiy large, rounded ; peristome continuous, thin. No operc. 



Animal with a large oblong foot ; margin of the mantle developed all 

 round, and more or less reflected over the shell; giUs 2; head broad; tentacles 

 subulate, blunt, far apart ; eyes on prominences at their outer bases. Carni- 

 vorous. Lingual dentition like trivia (fig. 15, B). 



