HELIX-HELICOPHANTA. 59 



Section I. HELICOPHANTA (Beck) Albers. 



Helicophanta (in part) BECK, Index Molluscorum, p. 46, 1837. 

 ALBERS-MARTENS, Die Heliceen, 1st edit., p. 148. PFR. Noment. 

 Hel. Viv., p. 169. 



This Madagascar group contains more very large Helices than any 

 other. The shells are characterized by their great size, either 

 lengthened, bulimiform, or depressed, and of an oblong, transversely 

 inflated shape. The volutions increase very rapidly in size ; the last 

 one descends deeply in front. The surface is nearly always finely 

 granulate or malleated; the nuclear whorls are several in number, 

 and attain a size exceeding one-third the greatest diameter of the 

 adult shell. The post-embryonic growth consists of not more than one 

 and one-half whorls, frequently less. 



The species vary from depressed, broadly heliciform, to elongated, 

 Bulimus-shaped. They fall into groups as follows : 



I. Heliciform species, either umbilicated or imperforate, much 

 broader than higher ; the columella proper consisting of a very 

 short curve and a small pad of white callus spread upon the base, 



Group of H. cornugiganteum* 



II. Bulimiform species ; imperforate, generally nearly as high or 

 higher than broad ; the columella rather long, straight or gently 

 arcuate, not terminating in a little pad, but more or less deeply 

 entering. 



a. Shell broader than high, rather thin. Group of H. magnified. 



b. Shell broader than high, thick and ponderous. 



Group of H. gloriosa* 



c. Shell decidedly higher than broad, columellar lip reflexed. 



Group of H. goudotiana. 



d. Shell lengthened, bulimiform, thick, columellar lip obtuse, not 

 reflexed, Group of H. farafanga* 



Group of H. cornugiganteum Chemn. 



This is a group of closely allied forms, very variable and difficult 

 to distinguish. I have not seen the true H. vesicalis, nor H. gues- 

 tieriana. The other species lie before me. Of these, cornugigan- 

 teum and betsileoensis are openly umbilicate, the former having 

 smooth, the latter decidedly granulate parietal callus and columel- 

 lar lip. H. guestieriana, bicingulata and ibaraoensis are imperforate 



