MOLLUSCA OF INDIA. 209 



Subgenus Ibyccts, Heyueraann. 

 (Continued from Vol. I. p. 242.) 



On further reference to Heynemann's drawing of the teeth of the 

 radula I have come to the conclusion that Ihycus Jissidens, Heyn., 

 is a species allied to Dimjella minuta, G.-A., from Assam, and 

 therefore must be considered to belong to the family Durgellidse, 

 certainly as far as the radula is concerned ; so with this radula as 

 a guide, there is every probability that /. Jissidens will turn up 

 again in Sikkim, provided Schlagintweit's locality is correct. As so 

 much of the single specimen Heynemann had to deal with was in a 

 decayed state, it is advisable to await its rediscovery to see how far, 

 besides the radula, it agrees with D. minuta of Assam, or even the 

 Celebes species of Leptodontarion previously referred to. 



The shell of D. minuta has 2| whorls ; the small anterior part 

 figured of the shell of /. Jissidens looks more like that of a spatulate 

 form. 



For the present the safest course is to retain Ilnjcus for the 

 Indian Jissidens type alone, leaving Leptodontarion for the Malayan 

 alhacuminatus and allied species, 



I have now to unsay, and undo, much of what I wrote in 1888, 

 on pp. 239-241 of Vol. I. At that time I laid too much stress on 

 the shell of I. Jissidens, or what remained of it, being spatulate, like 

 that of Girasia sikkimensls, and I overlooked the figured radula. 

 With this in mind, on p. 239 I made Ibycus a subgenus of Girasia, 

 and in it included some five species : — 



Girasia sikkimensis, G.-A. (Plate LTX. figs. 2, 2 a, animal ; 



2 b, shell.) 



G. sikkimensis, var. maimvarinf/i,G.-A. (Plate LIX. figs. 3, 3 a, 



3 6, animal.) 



G. cinerea, G.-A. (Plate XL. fig. 8, animal from life.) 



G. cacharica, G.-A. (Plate LIX. figs, 4-4 6, animal and shell; 

 Plate LXII. figs. 5-5 c, radula and gen. org.) 



G. solida, G.-A. 



All these I now consider have no relationship with Ihycus, and 

 must remain under Girasia. 



Take the first, G. sikkimensis. Compared with Jissidens, the 

 radula, a far more important character than the shell, is like that 

 of Austenia gigas {vide Vol. I. p. 239). 



Mr. T. D. A. Cockerell has been led away by shell-character 

 also : see a paper by him, " Notes on Slugs," Ann. & Mag. Xat. Hist, 

 vol. vii. Xo. 37, Jan. 1891. In his main Division B ("Shell more 

 or less whorled, but not truly Vitrinoid ; Avhorl subrudimentary) " *, 



* I cannot endorse the view that in shells of the Helicarion type a slight 

 addition of half or one whole whorl (making it, conchologically speaking, 

 " truly Vitrinoid ") is sufBcient reason for creating a new genus. A single 

 conchologieal character is thus made of enormous weight, while all the truly 

 important coitipliealecl internal organs of the animal are ignored. This applies 

 equally to a rudimentary shell like Girasia and the intermediate forms passing 

 into Austenia of the typical yigas shape. 



