216 HELICOSTYLA. 



Group of C. t her sites. 



C. thersites Brod., vii, 104. C. malleata Q. & M.. Nachr., '93, 



174. 



Genus HELICOSTYLA Ferussac. 



Helicostyla FER., Tabl. Syst., p. 46, in part. BECK, Index Moll., 

 p. 36, 1837, in part. ALBERS, Die Hel., 1850, p. 104. H. &. A. 

 ADAMS, Gen. Rec. Moll., ii, p. 191. MARTENS, Die Hel., p. 175, 

 type H. mirabilis Fer. Cochostyla FER., Tab. Syst., p. 47, 1819. 

 SEMPER, Reisen in Arch. Phil., Land Moll., p. 164. PILSBRY, 

 Man. Conch., vii, p. 92. Includes the groups Chlonea, Corasia, 

 Crystallopsis, Axina, Pfeifferia, Calocochlia, Helicostyla, Orustia, 

 Cochlodryas, Orthostylus, Helicobulinus, Ptychostylus, Phengus, 

 Eudoxus, Hypselostyla, Canistrum, Prochilus, Chrysallis, etc. 



For anatomy see SEMPER, Reisen im Archip. Phil, and PFEFFER, 

 Jahrb. Dm. Ges., 1878, p. 195. 



Shell varying from depressed, helicoid, to elevated and bulimoid, 

 imperforate, with solid columella (except in Crystallopsis and Chry- 

 sallis*) ; surface smooth or roughened, usually covered with a thin, 

 transparent cuticle, often porous in places when it becomes white and 

 opaque, producing the " hydrophanous" pattern which ornaments 

 most species, and which disappears upon wetting the shell. Aper- 

 ture toothless, but sometimes having a columellar twist or trunca- 

 tion ; the lip reflexed (but simple in Pfeifferia'). Type H. mirabilis 

 Fer. (see pi. 53, fig. 1-11). 



Foot without pedal margination ; a small left body-lappet often 

 developed ; kidney elongated. (PL 54, fig. 10, H. festiva ; pi. 54, 

 fig. 5, H. monticula). 



Jaw ribbed (pi. 54, fig. 6, H. butl&n). 



Radula with bluntly pointed or truncated mesocones on middle 

 and lateral teeth, without trace of side cusps. Marginal teeth hav- 

 ing the entocone indicated by a split in the broad inner cusp, a 

 small simple ectocone being developed. (See pi. 54, fig. 11, H. 

 aegle; pi. 54, fig. 12, H. pulcherrima. 



Genital system : Penis moderately long, passing into an epiphal- 

 lus which bears the retractor; flagellum wanting. Dart sack short 

 and globose, seated on atrium or low on vagina, bearing an accessory 

 sack into which the mucus gland opens. Mucus gland globular or 



