MOLLTJSCA OF INDIA. 201 



Subgenus Leptodontarion, P. & F. Sarasin, of Helicarion. 



Type : albacuminatus, P. & F. Sarasin, Die Landmoll. v. Celebes, 

 pp. 124, 125 (1899): shell, pi. xvii. figs. 148, 148 « ; radula, pl.xxviii. 

 fig. 280. 



Second species : coriaceus, P. & F. Sarasin : radula, pi. xxviii. 

 fig. 281. 



The brothers Sarasin, in the above fine work, created this sub- 

 genus of Helicarion, based on the great number of teeth in the row 

 and the similarity of the teeth throughout. 



A striking resemblance is found between these species inhabit- 

 ing Celebes and my DurgeUa minuta from the Dafla Hills (Vol. I., 

 PI. XXXIX. figs. 1-6), and the Sarasins notice this on p. 118. 



Their description of the animal corresponds. Tlie right shell- 

 lobe broad and broadly oval ; the left also broad, but towards the 

 back part narrowing out; the foot truncate, with a little horn. 

 The radula is precisely the same in both forms under comparison, 

 and although the Sarasins do not give the number of teeth in the 

 row, yet their general description of the radula exactly describes 

 the DurgeUa type and how entirely different it is to other species 

 included in Helicarion. The middle tooth is small, only a single 

 point almost rudimentary ; the side teeth are narrow, close together, 

 bicuspid ; the teeth stand in very long uneven lines. One may 

 describe the radula as composed of the lateral teeth alone, the out- 

 side or marginals being absent. 



They quote Semper on Helicarion, as pointing, out that in the 

 diff'erences in the jaw, in the radula, and in the generative organs 

 the shell does not go with them ; and this is the case with the shells 

 of Helicarion and Leptodontarion. They place H. incertus in it, but 

 consider H. tigrinus doubtful. I include DurgeUa hosei, G.-A., 

 from Borneo also. 



Far removed from other forms of Helicarion, Leptodontarion is 

 an excellent, well-defined subgenus, and together with DurgeUa 

 (typical) I have placed it in the subfamily Durgellinae (Vol. I. p. 253 

 and Vol. II. p. 60). 



This peculiar type of radula — its minute teeth may be counted 

 by hundreds in the row in some species — is almost as broad as it is 

 long, very different to the ribbon-like form. It follows ihat the 

 buccal mass is short, globose in shape, and rounded at the back, 

 presenting a marked departure from the same parts in other genera 

 of the Zonitidse. With this radula is associated a very thin mem- 

 branaceous jaw, also very different from tlie usual solid oxygnathous 

 jaw of the same family. 



Blanford considered that the Southern Indian DurgeUa dekhan- 

 ensis, G.-A., and D. levidensis, together with D. chrisiiance, should 

 form another genus. 



