CONCHOLOGY. 



117 



N. consolidata.* N. pusilla.* 



N. duplicata.* N. triseriata.* 



N. heros .♦ ^ / N. rugosa.* 



FAMILY XII. 



Jaxthinea. One genus. 



1. Genus Janthina. Pi. XI. 



Animal. Of oval form, spiral, provided Wxih. 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, 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 whorls ; 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 Xin. 



MACI{osT03IIA^'A. Four genera. 



1. Genus Sigaretiis. 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- 



