FAUNA OF THE INLAND SEA OF SINGQORA. 9[T 



(D. eontradeng) is interest! n<j in that it is also found in Perak and 

 Sumatra, but is represented in Caiuboflia and other countries to the 

 east of tlie Gulf of Siaui by distinct local races. 



The two most interesting genera of bivalves of this region, 

 however, were found only in the open lake. They are Modiola of the 

 family Mytillidae or true mussels and Scaphula of the family Arcidae. 

 'J he former genus is essentially a maiiiie one, and has been dredged at 

 considerable depths in the Bay of Bengal. In the rivers and lagoons 

 of India and Burma certain species make their way well into brackish 

 water and can even exist for periods in pure fresh water, while further 

 east, in Siam, Cambodia and Java, allied forms have become wholly 

 fluviatile. Finally, M. lamstris was discovered in a lake in the centre 

 of China. The species found in the Ta'^ Sap was described some years 

 ago by E. A. Smithl, from specimens collected by Dr. R. Evans and 

 myself at the Koh Sih-Ha, as M. evxnsL It is very abundant on 

 rocks, dead tree-trunks and weeds in the neighbourhood of these 

 islands, but I found no specimens in the outer lake that I could assign 

 to it with certainty. 



Sfaii]i.ala is a genus hitherto only known from Indian and 

 Burmese river-systems that open into the Bay of Bengal. It is a 

 dwarfed and slight!}' modified derivative of the marine genus Area, 

 some species of which ( notably A. fjranosa) iiabitually make their way 

 into brackish water. The Tale Sap species is distinct from any of the 

 Indian or Burmese forms. It is common on weeds all over the inner 

 lake and occurs, much more spai'inglv, on stones in the outer lake 

 round Koh Yaw near Singgora. 



Inserts. I had no time to collect insects seiiously in any part 

 of the Tale Sap, but two species of surface-bug ( Hydrometridae ) were 

 observed at diffei-ent places in the inner lake. Close to the edge near 

 Lampam the widely distributed Gerris spinolae was abundant, while off 

 Pak Pa3'un, at the mouth of the main channel connecting the two parts 

 of rhe lake-system, ILiloItates sex'ualis was by no means uncommon. 

 The latter was described by DistantS, from an estuary opening into 



1. Sinitii, Joiint. CiH-h. vol. X, p. Zi^A, fig. (1003) 



2. Di.stiiiit, "Hliyniliota Ilctt'iopti'm " in .\iinaiicl;de and nol)insotrs 

 F>iMiciiU Miil<ii/eii.<(:i, Zulfl.igy, vol. I, p iT.S, [.l w, tigs. 10, 10a, lul., (iyj3). 



VOL. II. i>i;('. itMi:. 



