CONCHOLOGY. 109 



foot, accompanied with a vesicular subcartilaginous mass, and 

 natatory appendages on each side ; head very thick ; tentacula 

 scarcely at all contractile ; eyes situated beneath the extremity of 

 long peduncles placed at the external side of the tentacula, and 

 appearing to form a part of them ; mouth at the extremity of a 

 very thick proboscidiform muzzle, between two vertical, subcarti- 

 laginous lips furnished with sharp spines. 



Shell. Of a beautiful violet colour, found in numbers floating 

 on the surface of the ocean, suspended by a vesicular appendage 

 which gives a rich purple stain. Extremely thin and fragile, spire 

 low, lateral, pointed, with subcarinated v/horls ; aperture large, 

 subangular, modified by the last whorl of the spire, edges dis- 

 united, the left formed by the columella, which is straight, con- 

 tinuing beyond the base, right edge sharp, with a sinus in the 

 middle. Inhabits the Atlantic Ocean. Three species. 



Janthina naticoides. Janthina communis. 



J. exigua. 



FAMILY XIII. 



Macrostomiana. Four genera. 



1. Genus SigareUis. PI. XI. 



Animal. Body oval, flat beneath; edges of the mantle ver- 

 tical, thin, extending beyond the body in all directions, sloped 

 anteriorly ; the mantle itself dilated superiorly. 



Shell. More or less thick, internal, without colour, much de- 

 pressed, with a short, low, lateral spire ; left edge of the aperture 

 trenchant ; two lateral muscular impressions very distant. In- 

 habits the Indian Ocean. Four species. 



Sigaretus convexus. Sigaretus cancellalus. 



S. Haliotoideus. S. laevigatus. 



2. Genus Stomatella. PI. XL 

 Animal. Unknown. 



Shell. Distinguished from the Stomatia by being destitute of 

 a tranverse rib, orbicular, oblong earshaped, imperforate ; aper- 

 11 



