FRESH- WATER FISHES OF SIAM, OR THAILAND 387 



gion; and in brackish waters of the Gulf of Siam off the mouths of 

 various rivers. 



This is the largest of the local mystids. Weber and de Beaufort give 

 a length of 35 cm. in the Indo-Australian Archipelago, but in Thailand 

 the hsh reaches more than 60 cm. in length and the thickness of a 

 man's thigh, and examples 20 to 35 cm. long are common. 



The usual color of the back is plain blackish or blackish green, the 

 underparts whitish, the fins mostly purplish or violet, the adipose fin 

 with a light edge ; there is, however, minor variation dependent on age 

 or size and locality. Thus, a medium-sized fish from the Menam Chao 

 Phya above Bangkok, April 24, 1926, had the caudal and anal fins black 

 and the adipose fin with a sharply defined black edge, a light green 

 submarginal area, and the center dark green; and several specimens 15 

 cm. long from the Meping at Chiengmai March 10, 1924, had the back 

 very light green, the sides golden, the belly white, the dorsal and 

 caudal fins pale green, the anal and ventral fins pink with a white edge, 

 and the pectoral fins yellow. 



The spawning season is not sharply defined and is protracted. A 

 fish 32 cm. long taken in the Chantabun River at Chantabun June 11, 

 1926, had very large ovaries with nearly ripe eggs 1 mm. in diameter, 

 while fish in spawning condition have been observed in the Menam 

 Chao Phya in November. 



A fish, 13 cm. long, taken in headwaters of the Menam Mun near 

 Pakjong January 19, 1925, had its stomach crammed with large red 

 ants. 



This species bears a large number of vernacular names along the 

 Menam Chao Phya and its tributaries. It shares with Tachysurus 

 the name pla kot^ often with a qualifying adjective, as pla hot mor and 

 pla hot chalong. In Northern Thailand, in the Meping and the 

 Mekok, the only designation heard is pla hot. On the Meklong at 

 Kanburi and Saiyok on the western branch of the Meklong, the fish 

 is called pla hlang or pla hot klang. About the northeast section of 

 the head of the Gulf of Siam, in the lower Bangpakong River and at 

 Cholburi, names applied are pla hot na., pla hot hao (^ao= white), 

 and pla hot lueng. Going down the Malay Peninsula, we find pla 

 hayeng and pla hot chong luang in use at Bandon, and pla hot in the 

 Tale Sap and the Tale Noi, while in Patani province the fish bears 

 the same designation as in Sumatra, ihan haung. 



MYSTUS PLANICEPS (Cuvier and Valenciennes) 



Bagrus planiceps Ctt\iee and Valenciennes, 1839, vol. 14, p. 421 (Java). 

 Mystus planiceps Fowler, 1935a, p. 104, fig. 30 (Bangkok) ; 1937, p. 148 (Bang- 

 kok, Tachin Rayong) ; 1939, pp. 40, 58 (Huey Yang, Trang). 



The claims of this species to a place in the Thailand fauna rest on 

 the existence in the British Museum of an adult specimen froni 



