XXV. REPORT ON A COLLECTION OF SUMA- 



TRAN MOLLUSCS FROM FRESH AND 



BRACKISH WATER. 



By B. Pr.^sh.^d, D.Sc, Assistani Superintendent , Zoological Survey 



of India, with an Infroductorv Note by N. Ann.'^ndale, D.Sc, 



F.A.S.B., Director. Zoological Survcv of India. 



(Plate XIV.) 

 Introductory Note. 



The collection on which this report h.is been basjd was made b\- Mr. J. K. A. 

 den Doop and w.is submitted to me lor examination. Afler a certain amount of 

 preliminary work I was oblig-ed by stress of official duties to hand it over to 

 Dr. B. Prasliad, who has worked it out in detail. The collection is very represen- 

 tative of the Molluscs of most types of fresh and brackish water in Sumatra. 

 Only the true lacustrine forms and the bivalves of brackish water are poorly 

 represented. The collection is particularlv rich in Gastropoda from streams in the 

 plains and manjjrove-swamps on the coast. It has been of great assistance to us in 

 working out similar elements in the fauna of the eastern districts of British India, 

 and we may claim it as fortunate that it has been possible to consider the Molluscs 

 of the two cotmtries together. 



The niolluscan fauna of Sumatra is now at least as well known as that of any 

 other similar area in the Eastern Tropics. It is verv much better known, for 

 example, than that of the Malay Peninsula or even that of many parts of Burma. 

 1 he number ol fresh- .uid brackish-water species that has been recorded from the 

 island is two hundred and fortv-six including sixty here recorded or described 

 lor the first time. Of the 246 species no less than 100 have been found in .Mr. den 

 Doop's collection. The thanks and congratulations of all malacologists are clue to 

 him, and we are particularly grateful in the Indian Museum for permission to retain 

 ii first set of the specimens. The remainder are to be sent to the Amsterdam 

 Museum. The fact that a large proportion of the material is preserved in spirit 

 v.ith the sofi parts intact is an interesting and important feature. 



We have to thank Prof. Max Weber of .Amsterdam not only for sending us 

 in exchange specimens of a large proportion of the species described by the late 

 Prof. R. von Martens from his own collections in the Malay .Archipelago, but 

 also for sending us on loan examples of the species of which no duplicates were 

 available. This has not onl\- rendered the report more at^thoritative but has 

 greatly lessened the labour of its preparation. [N. .Annan'dXle]. 



Introduction. 



Thi.s report deals witli a large collection of fresh- and brackish- 

 water mollusca ' made by Mr. J. E. A. den Doop in Sumatra ' during 

 the years 1916 — 1918. Details about it are included in the intro- 

 ductory note by Dr. N. Annaiidale at the beginning of the report 



' The collection also includes large numbers of marine and land-molluscs, 

 but these we are unable to deal with at present. 



- The collections were made onlv in the- northern pari of the '' Gouvernement 

 Oostkust van Sumatr.i " .nid on the Isle of Sab.ing. 



