6ASTEE0P0DA. 256 



Shells extremely like the recent phorus, are met with even in 

 the carb. limestone and lias. 



Lacuna, Turton. 



Etymology, lacuna, a fissure. 



Tijjpe, L. pallidula (PI. IX., Fig. 16). 



Synonym, Medoria, Gray. 



Shell turbinated, thin ; aperture semi-lunar ; columella flat- 

 tened, with an umbilical fissure ; operculum pauci-spiral. 



Animal; operculigerous lobe furnished with lateral wings and 

 tentacular filaments. Teeth ocusped; uncini 1, 2, dentated, 

 3 simple. Spawn [ootheca) vermiform, thick, semi- circular. 

 Eange, low water — 50 fathoms. 



Distribution, 16 species. Northern shores, Norway, Britain, 

 Spain. 



Fossil, 1 species. Glacial beds, Scotland. 



LiTioPA, Eang. 



Etymology, litos, simple, ope, aperture. 



Type, L. bombyx (PI. IX., Fig. 2-1). 



Shell minute, pointed ; aperture slightly notched in front ; 

 outer lip simple, thin ; inner lip reflected ; operculum spiral. 



Distribution, 6 species. Atlantic and Mediterranean, on float- 

 ing sea-weed, to which they adhere by thi-eads. 



Fossil, 1 species. Pliocene (Crag). 



EissoA, Fremenville. 



Etymology, named after Eisso,* a French zoologist. 



Ttjpe, E. labiosa (PL IX., Fig. 17). 



Synonym, Cingula, Flem. 



Shell Taimite, white or horny; conical, pointed, many-whorled; 

 smooth, ribbed, or cancellated; aperture rounded; peristome 

 entire, continuous ; outer lip slightly expanded and thickened ; 

 operculum sub-spiral. 



The animal has long, slender tentacles, with eyes on small 

 prominences near their outer bases ; the foot is pointed behind ; 

 the operculigerous lobe has a wing-like process and a filament 

 [cirrus] on each side. Lingual teeth single, sub-quadrate, 

 hooked, dentat d; uncini 3; 1 dentated, 2, 3, claw-shaped. 

 They range from high-water to 100 fathoms, but abound most 

 in shallow water, near shore, on beds oifucus and zostera. 



Distribution, about 70 species. Universally distributed, but 



* It is much to be regretted that some modern naturalists have tried to find out and 

 bring nt us- the obscure genera of Eisso, and Uie worililess fabrications of Montfort 

 and Eafinesque, which had better have remained unknown. 



