HELICELLA. 



259 



H. explanata shows clearly the transition between the species with 

 one and those with two dart sacks. The second sack is formed by 

 splitting of the first. In some other species of this keeled group the 

 sack is apparently single and simple, as Schuberth has figured it for 

 H. syrosina. 



Jacosta is in all probability a purely artificial group, containing 

 keeled forms which have arisen from several diverse stocks of un- 

 keeled Helicellas; but only a thorough study of the shells and 

 anatomy of many species can demonstrate the true origin of the 

 several forms. 



H. agona Anc. 

 H. amanda Rm. 



limbata Phil, 

 v. dormiens Ben., iii, 252. 

 v. iiisularis Iss. 



H. amphiconus Malz., viii, 180. 

 H. argonantula W. & B., iv, 42. 



typica and canariensis Mss. 



renati Dautz. 



H. arianensis Bgt., iii, 253. 

 H. barceloi Hid., iii, 257. 

 H. barneyana Anc., viii, 183. 



theodori Anc. ms. 

 H. biangulosa Mts., iii, 178. 

 H. boissyi Terv., iii, 254. 



v. frater D. & H., iii, 258. 

 H. brondeli Bgt., iii, 255. 

 H. cardonse Hid., iii, 258. 

 H. caroli D. & H., iii, 258. 

 H. cavannse Paul, iii, 259. 



v. scissa Paul. 

 H. cavimargo Mts. 

 H. cisternosi Hid., iii, 259. 

 H. columbina West. 

 H. corrugata Gmel., iii, 252. 



rugosa Chem. 



groyana Fer. 



gargottce Phil, 

 v. pleurischurra Bgt. 

 v. chonomphala Bgt. 



H. crenimargo Kryn., iii, 252. 



piatigorskiensis Bayer. 

 H. depressula Parr., iii, 256. 

 forms globulosa, flammulata, 

 zonata, fulva, compressa Bgt., 

 exserta, murustagensis West. 

 H. douraeti Bgt. 



v. lacosteana Mor., iii, 255. 

 H. eminens West., viii, 180. 



syrensis v. exserta Mts. 

 H. enica L. & B., viii, 182. 

 H. eugoniostoma Bgt. 

 H. explanata Mull., iii, 255. 



albella Dr. 



/. minor Bgt. 



/. subscalaris Bgt. 

 H. filimargo (Z.) Rm., iii, 251. 



taurica Par,tch. 



chersonesica Miihl. 

 H. finitima Mor., iii, 241. 

 H. gradilis Mts., viii, 179. 

 H. graja West. 



v. philesia West. 

 H. grauostriata Mouss., iv, 43. 

 H. grovesiana Paul, iii, 254. 

 H. hamudie Kob., viii, 182. 

 H. hariotiana Bgt. 

 H. henoniana Bgt., iii, 254. 



v. agriuneusis Kob. 

 H. homeyeri D. & H., iii, 257. 



