president's addeess. 253 



which, goes no further. The form of the interior or moukl depends 

 much on the stage of development reached by the spermatophore, 

 and this modifies the external outline. I do not think this is 

 sufficiently taken into consideration by certain malacologists, who 

 are given to see in some genera of the mollusca they are studying 

 differences which to them are specific, but which truly are extremely 

 slight variations in the external outline of the reproductive organs. 



Keturning again to geographical distribution, I have to notice 

 another form inhabiting Ceylon, viz. the irradians of Benson, 

 for which I cannot find a prototype. In its jaw and radula there 

 are interesting differences as compared with other species, and its 

 reproductive organs are far simpler than one might have expected. 

 The tentacles are nearly white in spirit specimens ; in life I believe 

 they are yellow. On these grounds I have had to create a new 

 subgenus, Ratnadcipia,^ for its reception. 



Smaller species from this part of India will be alluded to further on. 



I now pass on to genera occurring in Burma and the Malay 

 Peninsula, etc. First in importance comes Hemiplecta of Singapur 

 (the type being H. Humphrey dana)^ a genus which has suffered much 

 from the lack of adequate definition of its characters, and on the 

 ground of shell character alone has either been made the receptacle 

 for forms from Peninsular India, or been itself merged in the genus 

 Rhysota. This was Stoliczka's course when he placed H. Cyniatium of 

 Penang in Rhysota. It agrees in every particular with H. Humphrey- 

 siana. In the presence of shell-lobes on both sides, in the radula and 

 generative organs, it is qnite unlike any South Indian form. This 

 genus, represented by If. densa, extends to Borneo, and includes 

 several other species in that very distinct province of Malayana. 



Cryptosoma as a subgenus is represented by. several large species from 

 Burma, Siam, etc. The points that distinguish this from kindred forms 

 are not many ; there is scarcely any change in the generative system, 

 in its general outlines, but the spermatophore is armed with spines, 

 while such are absent in Girasia and Austenia. The jaw and radula 

 differ altogether, as the formula of the latter shows. It has lately 

 been claimed that this genus is found in Calcutta, and Mr. Collinge 

 has described and figured a small species and named it after me. 

 Unfortunately, all description of the jaw and radula is omitted, and 

 I should expect the number of teeth in the row would have conformed 

 to A. Ben&oni had they been examined, while the genitalia figured 

 were not quite complete. The shell is remarkably like A. Bensoni, 

 which is fairly common and well known in Calcutta. 



I would add a word or two of warning concerning Calcutta species. 

 Many circumstances conspire there to promote the introduction of 

 foreign species. The extensive Botanical Garden is a good place for 

 shells, and consignments of plants are constantly being received there 

 from every part of India and of the world, so that a transported shell 

 might very well become established, and spread far and wide, as some 

 have done in this very locality. 



^ One of the old names of Ceylon : ratna, ' a jewel,' and dwipa, ' an island.' 



