10 LAND AND FRESHWATER 



as to the close relationship, especially shown in the genitalia. 

 Diakia did not occur among the Abor coUeetions, unless it shall 

 eventually turn out that Bensonia{'i) ahoreiisis, Eec. lud. Mus. 

 vol. viii. p. 596 (text-fig. 1), has similar anatomy. In slioll 

 character it is unlike that of any Indian Ueuus I have seen ; but 

 1 had only one specimen to deal with. 



For a knowledge of the peculiar anatomy of Dicikia, we have to 

 go to Semper, where he deals with what was then known as 



Ai-iujjhania riimpliii in lleisen, pi. iii. tig. 18. 



rurt'(/uttatri, var. Sj'arsa „ „ tig. 17. 



nemo''e,i-:is ,, ,, tig. 19. 



striata, Gra,\ ^naiiinoides, I3s. „ tig. -!i a-h. 



He gives heautilul figures of the genitalia, so unlike those of any 

 strictly Indian Genus. 



Our knowledge of the Assam Land MoUusca is very imperfect ; 

 much has still to be dime, with small chance of our knowing more 

 under present conditions. In fact, discovery of species of great 

 interest is sheer luck ; unless the conditions are exceedingly good, 

 perfect ia fact, nothing is found. To e.xemiilify this, I will give 

 an experience of my own when in the Dafia Hills. 



Shengorh Peak was one of my Trigonometrical Stations, and 

 I had to clear tlie forest hefore 1 could commence observations, 

 llain set in soon after pitching cam-]) ; so I had plenty of leisure to 

 collect in Natural History. The wet brought out the shells ami 

 slug-like forms, and I had a husy time making drawings and taking 

 lujtes of colour and size. I secured what in drier weather 1 should 

 never have got, certainly not alive ; among them was this unique 

 Genus Staff'onMa, whose neaiest relative known to us is found at 

 Cliantaboon in Siam. It doubtless occurs at many intermediate 

 jilaces which have yet to be discovered, when its possible ancient 

 connection with Assam may be explained. 



This is the history of a visit to one high point, one which over- 

 looked the great broad valley of the Subansiri, extending far hack 

 to the base of the snowy range, away to hundreds of peaks covered 

 with primeval torest. The imagination fails to picture what the 

 result of exploration would be, combined with knowledge of how 

 and what to collect. In these solitudes Nature reigns supreme ; 

 one does not often find such a spot — seldom visited by man, 

 never lived in by him. 



The birds on this Peak were fearless. I was quite struck by the 

 behaviour of a beautiful little SutJwra, which kept hovering about 

 my head and would jjerch on a twig a yard from :ny face. 



Starting with Sikhim and the valley of the Teesta, where species 

 are numerous, I t ike in succession going eastward the great valleys 

 of the Eastern Himalaya to the Erahmaputra, they go far back 

 ill geological time — are older, in fact, than the Sivaliks, for down 

 their courses all the waste of the Himalaya has passed either to the 

 sea, as in the case of the Teesta, or to build up the above formation. 

 The vast thickness of these Tertiary rocks, originally deposited not 

 far above sea-level, the basement beds being even marine, as near 

 Samaguting, is well seen on the .Vssam Range south of the Brahma- 



