178 HELICID^E. 



seminis on a long, simple duct ; penis short, with the retractor 

 muscle inserted low, and ending in a flagellum and the vas 

 deferens. Nervous and retractor systems Helicine." {Pilsbry.} 



The genus Amphidromus as originally proposed by Albers 

 included several species since then referred to Helicostyla. Von 

 Martens was the first correctly to define the group, which owes 

 its name " to the peculiar circumstance that several species occur 

 either dextral or sinistral, with equal frequency ; others are 

 sinistral only, still others dextral." Many of the species were 

 originally described as Bulimi, while the group remained to be 

 considered as a section of the genus Bulimus, until Pilsbry in 1900 

 proved that the genus did not belong to " the Bulimulidce, but to 

 that group of Helicidce called Epiphallogona, of which the genera 

 Chloritis, Obba, Planispira, and Papuina are leading members." 



The Indian region contains bnt a limited number of species, 

 which is not surprising when we bear in mind the fact that it is on 

 the confines of the area of distribution of the genus. 



Bulimus andamanensis (coll. Mousson) has been referred to by 

 von Martens in Preuss. Exp. Ost-Asien, 1867, p. 339, as from the 

 Andaman Islands ; it was described and figured by Pfeiifer in 

 Novit. Conch, ser. 1, iv, 1871, p. 35, pi. 116, figs. 7-10, and 

 referred to Amphidromus inversus as a small form by Pilsbry (Man. 

 Conch, ser. 2, xiii, 1900, p. 169, pi. 56, figs. 94-97). Pfeiffer 

 himself stated that it approached B. inversus, and might perhaps 

 be regarded as a dwarf variety. Pulton states (A. M. N. H. ser. 6, 

 xvii, 1896, p. 70) that the small form of A. inversus has been 

 found at Sarawak and Sirhassen Island by Everett, and as no 

 Amphidromus has been found in the Andaman Islands by recent 

 collectors, it must be assumed that the record is based on an error, 

 probably due to a mixing of labels. 



151. Amphidromus janus, Pfeiffer. 



Bulimtis janus, Pfeiffer, P. Z. S. 1852, p. 85; ibid., Conch.-Cab., 

 Bulimus, 1854, p. 156, pi. 48, figs. 1-4 ; Gassies, Act. Soc. Linn. 

 Bordeaux, xxiv, 1861, p. 253, pi. 5, fig. 5. 



Bulimus (Amphidromus) janus, Pfeifi'er, Malak. Blatt. ii, 1856, 

 p. 147 ; Hanley & Theobald, Conch. Ind. 1876, p. xi, and foot- 

 note 1, pi. 19, fig. 5 (atricallosus in explan. plates, p. 10). 



Cochlostyla (Canistrum) janus, Adams, Gen. Rec. Moll, ii, 1855 

 p. 143. 



Amphidromus janus, Nevill, Hand List, i, 1878, p. 126 ; Pilsbry, 

 Man. Conch, ser. 2, xiii, 1900, p. 156, pi. 58, figs. 14-18. 



Original description : " B. testa imperforata, dextrorsa vel sini- 

 strorsa, subfusiformi-oblonga, solida, vix nitidula, lutea fasciis 3 

 extus opace viridibus, intus nitide atro-castaneis, peristoma non 

 attingentibus, basali latissima, varicibusque castaneis sparsis ornata ; 

 spira conica, acutiuscula ; anfractibus 6-7 convexiusculis, ultimo 

 |- longitudinis subaequante, basi attenuate ; columella verticalis, 

 stricta ; apertura obliqua, semiovalis, basi subangulata ; peristo- 



