94 DR. NELSON ANNANDALE ON THE 



Patani Bay en the same coast. The head of a water snake (ITerpeton) 

 taken near the mouth ot the Patalung River was covered with the 

 eggs of a bug of the same family. 



Crustacea. There are comparatively few Crustacea in the lake. 

 The only crab observel was a species of Petamonidae— an almost ex- 

 clusively fluviatile and lacustrine family. It appears to belong to a 

 form (Potamon c/p.rmaini) common in Siam and the northern part of the 

 Mala}' J'eiiinsnla, and is found in considerable numbers both at the 

 edge of the lake and in streams, rice-fields, etc., in the vicinitj'. Small 

 shrimps belonging to several species of the family Atyidae — also a 

 freshwater family — abound among weeds in several places. One of 

 them has already been described bj' Lanchesterl as Caridina ijracil- 

 lima ; the tj-pe specimens were taken by Dr. Evans and myself at the 

 mouth of the Patalung River in 1899. Inside this river several species 

 of Palaemon are caught as food, ranging in size from the gigantic P. 

 carcinux, the largest of all the freshwater prawns, which occurs all over 

 tropical and subtropical Asia east of Arabia, to the little P. lancliesteri 

 de Man (= P. pancidens Lanchester ), which is only known from 

 Singgora and Patalung. Palaemon is again a freshwater genus, though, 

 as we shall see, certain species migrate into brackish water or can 

 even live in the sea. 



In the central part of the inner lake no true crabs or shrimps 

 were found, but a " Schizopod " of the family Mysidae was taken in 

 small numbers. Though this family is mainly marine, certain species 

 have established themselves, both in Europe and in Asia, in brackish 

 and even in fresh water. The Tal6 Sap form occurs very sparingly 

 if at all in the outer lake and would, therefore, seem to have become 

 strictly lacustrine in habits. Neither Amphipods nor Isopods are 

 abundant in this region, either near the edge or in the central parts. 

 A single specimen of the curious genus Quadrivisio, found in brackish 

 water in India and E ist Africa and common in the outer lake, was 

 obtained at the mouth of the Patalung River, while a narrow-bodied 

 Isopod was found fairly common in the bed of the lake. 



The Plankton of this region is probabl}' scanty at all sea- 



1. I^anclii'stor, Fror. Zunl. Soc. London, 1901, p. 5C0, pi. xxxiv, fig. 1. 



JOUKN. NAT. HIST. SOC. SU.M. 



