HELICAEION. 179 



indefinable nature one is so often confronted with in shells of 

 this type. Finally, on dissection, one (richilaensis) was found to 

 be a Macrochlamys with the characteristic shell-lobes ; the other 

 (bhutanensis), above described, had none, and, besides, very different 

 genitalia with no amatorial organ, thus representing two quite dis- 

 tinct genera.] 



[Subfamily HELICARIONIN^E. 



Helicarioninge, Godwin-Austen, Mol. Ind. i, 1883, p. 146. 



Typical genus, Helicarion^ Fer. 



Range. Australia, Indo-Malay, Japan, China, islands of the 

 Pacific, and westward to Siam, Burma, and India. 



This large subfamily contains many well-defined and interesting 

 generic divisions. The similarity of the shells of many species to 

 those of the palaearctic genus Vitrina led at first to their being 

 placed by authors in that very distinct genus. The animal has 

 broad shell-lobes more or less covering the shell, and a tail-gland 

 is characteristic of the subfamily. The generative organs are 

 simple, the amatorial organ absent in many. The jaw is oxy- 

 gnathous. The radula ranges from one similar to that of the 

 Macrochlamyince, with teeth 80-100 in the ow, laterals bicuspid, 

 occasionally tricuspid, to another with very numerous teeth, as 

 many as 300-400, in the row, of simpler form, with a minute 

 central tooth, and approaching but not so pectinated as those 

 of the Durgellince. The animals differ widely from each other in 

 the different genera. The shells are of a rudimentary type, 

 thin, delicate, few-whorled, and are of little use in generic 

 determination.] 



[Genus HELICARION. 



Helicarion, Fr. Prod. (Hist. Nat.} p. 23 (1821). 

 Austenia, partim, Godwin-Austen, Mol. Ind. i, 1883, p. 148. 



Type, H. cuvieri, Fer., from Australia. 



Mange. Indo-Malay and Australasian Regions. 



In the type genus the animal has the keel of the foot flattened. 

 In the generative organs the amatorial organ is absent, the penis 

 is attenuate, a long epiphallus and a very long kale-sac. The shell 

 of 2| whorls, the last much expanded and more closely wound 

 near the protoconch than in the Indian forms of the subfamily. 



In Helicarion various authors have placed quite a large assem- 

 blage of species, some of which, as the animals have become known, 

 have very rightly been made the types of new genera. The shells 

 vary in form from that of the type species H. cuvieri, and while all 

 are thin, more or less membranaceous, some are even helicoid with 

 high spire and with four or five whorls. South-African forms 

 placed in Helicarion, such as H.lmdsonice, Benson, depart much from 

 the typical form. Perhaps the most distinctive group are those 



N2 



