1. Genus Janthina. Pl. [XI].
Animal. Of oval form, spiral, provided with a circular concave 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, subcartilaginous 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 whorls; aperture large, subangular, modified by the last whorl of the spire, edges disunited, the left formed by the columella, which is straight, continuing beyond the base, right edge sharp, with a sinus in the middle. Inhabits the Atlantic Ocean. Three species.
- Janthina naticoides.
- J. communis.
- J. exigua.
FAMILY XIII.
Macrostomiana. Four genera.
1. Genus Sigaretus. Pl. [XI].
Animal. Body oval, flat beneath; edges of the mantle vertical, thin, extending beyond the body in all directions, sloped anteriorly; the mantle itself dilated superiorly.
Shell. More or less thick, internal, without colour, much depressed, with a short, low, lateral spire; left edge of the aperture trenchant; two lateral muscular impressions very distant. Inhabits the Indian Ocean. Two species are found in S. America. Six species.
- Sigaretus convexus.
- S. Haliotoideus.
- S. cancellatus.
- S. lævigatus.
- · · · · ·
- S. perspectivus.*
- S. maculatus.*