FRESH-WATER FISHES OF SIAM, OR THAILAND 363 



fish is easily recognizable by its very broad and strongly depressed 

 head, rather short body, steep dorsal profile, and short barbels, com- 

 bined with the union of the vomerine teeth into a single quadrate patch 

 and detached elongate patches of palatine teeth which with the vomer- 

 ine form a regular crescent. The type is in the U. S. National Museum, 

 No. 90308. 



PANGASIUS POLYURANODON Bleeker 



Pangasius polyuranodon Bleeker, 1852 (55), p. 425 (Baudjermassing, Borneo). — 

 Sauvage, 1883b, p. 154 (Mcuam Cbao Pbya). — Weber and de Beaufort, 1913, 

 vol. 2, p. 257 (Siam). 



The range of this species extends from Java, Borneo, and Sumatra 

 to Thailand and Cambodia. The fish haunts the lower reaches of the 

 Chao Phya and Bangpakong Rivers, and has not been recorded from 

 other Thailand streams. In the first-named river it has been taken at 

 Paknam, Bangkok, Nontaburi, and Koh Yai. Specimens were ob- 

 tained in June from a pongpang net in the Bangpakong above the 

 village of the same name near the river's mouth and in July from a 

 seine at a point 8 miles from the Gulf of Siam. 



This is one of the two pangasiids that have been reported from the 

 Gulf of Siam. Two specimens about 45 and 52 cm. long were obtained 

 in August from the gulf off the mouth of the Menam Chao Phya. As 

 this was during the flood season, when an enormous volume of fresh 

 water was pouring out of the river and extending far off shore, the 

 occurrence of a fresh-water fish in that area was of no special signifi- 

 cance. Both of these specimens had small bivalve mollusks in their 

 stomach. 



Among the characters by which the species may be recognized are 

 the rather slender form (depth 5 to 5.3 in standard length) ; maxillary 

 barbels extending to or slightly beyond the base of the pectoral fins; 

 a large rectangular patch of vomerine teeth flanked by a small lenticu- 

 lar mass of palatine teeth ; and long anal fin with 35 to 40 rays. 



The fish is not very common, but occasionally a large catch is made 

 by the seine fishermen. In May 1928 many 30 to 40 cm. long reached 

 the Bangkok markets from the important fishing grounds at Koh Yai. 



The usually employed vernacular name is pla sawai. On the Bang- 

 pakong the fish is sometimes called pla sangkawang, a name said to 

 imply a fish inhabiting deep holes in the river bed, not to be confused 

 with pJa sangkawad. 



PANGASIUS SANITWONGSEI H. M. Smith 



Figure 82 



Pangasius sanitwongsei 5mith, 1931a, p. 29, figs. 13, 14 (Menam Chao Phya) . 



This interesting species is peculiar to Thailand. Its range is re- 

 strictec?, for it is a fish of the largest rivers, and is seldom, if even, met 



