14 



more than convex ; lateral line somewhat convex ; whorls five, 

 obsoletely striated across, regularly rounded ; color pale greenish, 

 yellowish, or slightly tinted with reddish, particularly on the body, 

 and margined above by an obsolete white line ; on the middle of 

 the body a white vitta revolves, sometimes obscure or wanting ; 

 aperture acute above, regularly rounded at the base, and extend- 

 ing from the centre of revolution or base of the column to an 

 equidistance between the base and the apex of the spire ; base of 

 the columellar slightly projecting into an obtuse angle ; exterior 

 lip whitish, reflected. 



Length one-fifth of an inch. Inhabits East Florida. Cabinet 

 of the Academy. Animal pale ; rostrum and tentacula blackish, 

 the latter with a white line ; eyes very black, elevated in the form 

 of a short tubercle ; length about equal to the breadth of the 

 shell ; foot not broader than the body ; tail rounded, or somewhat 

 acute ; operculum simple, not spiral, yellowish brown, minutely 

 granulated. 



This species we found in great numbers on what are called 

 Oyster-Shell Hammocks, near the mouth of the river St. John, 

 East Florida, in company with Polygyra septemvolva. "When in 

 motion the tentacula are elevated and depressed alternately, as if 

 feeling the way. 



This shell is certainly a Linnaean Helix, but according to the 

 improvements which have been made in Conchology since the time 

 of the Swedish naturalist, by Mr. Lamark and other systematists, 

 it is at once excluded from that genus and its congeners, by hav- 

 ing but two tentacula, and by its operculated aperture. With the 

 genus Cyclostoma, as it now stands, our shell has more affinity 

 than it has to any other, but a very distinct generic character is 

 observable in the aperture, which is not orbicular as in Cyclostoma, 

 but is almost semi-orbicular, greater in length than in breadth, and 

 the lips widely disunited. In addition to the characters usually 

 given of the animal of Cyclostoma, Mr. Cuvier remarks that the 

 tentacula are terminated by obtuse tubercles ; no such appendages 

 are annexed to the corresponding members of this animal. Upon 

 these considerations I have thought proper to construct the present 

 genus. 



