FAMILY 3. CYCLOSTOMACEA. 101 
though generally in damp places, not higher than two thousand métres 
above the level of the sea. Guilding, however, says, that the species found 
in St. Vincent scarcely ever descend below two thousand feet above the 
level of the sea, and that those in Barbadoes are found in situations how- 
ever exposed and dry. 
Many of the Helicine are characterized by having a slit in the margin 
of the aperture at the base of the columella, like the Pupine ; and Gray 
has considered this variation of sufficient importance to constitute the mark 
of a new genus, Alcadia ; we cannot, however, appreciate its generic 
value, because an indication of this slit may be traced in many species 
where it appears to have been filled up by the last deposit of enamel. 
The shell of Helicina may be described as being somewhat globose, 
with the spire either acute or a little depressed; the aperture is semi- 
orbicular, with the margins disjoined, and the lip is expanded, reflected, 
and sometimes indented with a slit or fissure near the columella; the 
columella is transverse, and callous at the base; and the operculum, 
which is horny, though often a little calcareous, is not spiral. 
Examples. 
Pl. CLXXXVI. Fig. 1. 
HeEticina varrIABILis, Wagner, Moll. du Brésil, pl. 16. f.3 to 5. Mo- 
ricand, Mém. de Genéve, vol. vii. p.448. Deshayes, edit. of Lamarck, 
vol. vii. p. 165. 
Helicina zonata, Sowerby, Jun. 
Pl. CLXXXVI. Fig. 2. 
Hexicina acurissima, Sowerby, Jun., Proceedings Zool. Soc., 1841. 
Thesaurus Conchyliorum, pl. 2. f. 92 to 95. 
Pl. CLXXXVI. Fig. 3 and 4. 
Hexicina apsprrsa, Pleiffer, Wiegmann’s Archives Nat. Hist., 1840. 
Sowerby, Jun., Thesaurus Conchyliorum, pl. 3. f. 103, 115, 124 and 
}25. 
Helicina variegata, D’Orbigny. 
