HELICINID^. 291 



animals of the Cyclophoridae, but are considerably more loco- 

 motive and lively ; in common with some other mollusks, as the 

 Neritidse and Ellobiidae, they possess the faculty of removing 

 the inner septa and columella of the shell. 



Helicina, Lam. 



Syn. — Ampullina, Blainv. Pitonillus, Montf. 



Distr. — 350 sp. West Indies, tropical America, Pacific 

 Islands, Australian Islands, Philippines. H. variegata, Orb. 

 (Ixxvii, 28). 



Shell globose, depressed or keeled, callous beneath ; aperture 

 squarish or semilunar; columella flattened; peristome simple, 

 expanded. Operculum shelly or membranous, squai'ish or semi- 

 ovate, lamellar. 



oiJGYRA, Sa^^ Shell subglobular or conic, spire and last whorl 

 of about equal height, peristome expanded. H. oacuUa, Say. 

 United States. 



PACHYSTOMA, Swainson. Shell conically depressed, carinated. 

 H agglutinans, Sowb. (Ixxvii, 29, 30). 



P(ENIA, H. and A. Adams. Peristome subdentate interiorly. 

 H. depressa, Gray (Ixxvii, 31). 



IDESA, H. and A. Adams. Peristome simple, sharp. H. rotunda^ 

 Orb. (Ixxvii, 32). 



EMODA, H. and A. Adams. Peristome simple, thick, obtuse. 

 H. /estiva, Sowb. (Ixxvii, 33). 



PERENNA, Guppy, 186t. Shell depressed, whorls Urate and 

 carinate. Operculum thin, suboval, concentrically striate, 

 nucleus subcentral. H. lamellosa, Guppy. Isl. Trinidad. 



DAWSONELLA, Bradley. Aperture small, lip thickened within, 

 columella with a wide-spreading linguiform callus covering the 

 axis. Carboniferous ; United States. H. Meeki, Bradley 

 (Ixxvii, 34). 



Trochatella, Swainson. 



Distr. — 34 sp. West Indies. T. C07iste?Zato, Morel. (Ixxvii, 35). 



Shell trochiform or globular-conic ; aperture subtriangular ; 

 peristome simple, expanded ; base not callous. 



VIANA, H. and A.Adams. (Rhynchocheila, Shutt. Hapata, 

 Gray.) Shell subcarinated ; lip with a superior sinus. T.regina, 

 Morel. (Ixxvii, 36). 



ScHAziCHEiLA, Shuttleworth. 



Distr. — 5 sp. West Indies, Central America. S. aZa^a, Menke 

 (Ixxvii, 3T, 38). 



Shell with spiral epidermal fringes ; peristome profoundly 

 incised at the suture. Operculum thin, testaceous, with an intra- 

 marginal rib. 



