384 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



The usual length of mature fish is 12 to 20 cm. The largest examples 

 observed have been 30 cm, long. 



It is essentially a fish of the lower courses of rivers. Specimens have 

 been examined from the Patani Kiver, the inner lake of the Tale Sap, 

 the Tapi River near Bandon, the Tachin River near Tachalom, and 

 various parts of the lower Chao Phya River. The only record of a 

 fish far from the sea is that of Fowler (1934a) for a specimen 11 cm. 

 long from the Meping at Chiengmai, Northern Thailand. 



The fish sometimes enters salt water off the mouths of rivers and 

 may be found there abundantly. Collections made for the Siamese 

 Bureau of Fisheries contained specimens from the Gulf of Siam off 

 the Banghia River in July, off the Tapi River in Bandon Bight in 

 September, and off Pakpoon, Nakon Sritamarat, in October. 



Thai fish conform generally with the description given by Weber 

 and de Beaufort. In a number of specimens, 12.5 to 16.5 cm. long, how- 

 ever, the mandibulary barbels do not extend on the anal fin but fall 

 considerably short of the anal origin. 



In a fish 17.3 cm. long from the Gulf of Siam off Bandon the left 

 maxillary barbel had been amputated at about its midlength and the 

 right maxillary barbel was represented by a stump that reached only 

 halfway to the eye; from the upper edge of this stump a new, very 

 slender barbel had grown and extended beyond the eye. 



The species shares with others of the genus the vernacular name fla 

 Jcayeng or pla yeng. In the Province of Patani, with its large Malay 

 population, the fish is called ikan haon^ a name bestowed on M. nemurus 

 in Sarawak {ikan haung in Sumatra). 



MYSTUS GULIO (Hamilton) 



Pimelodus gulio Hamilton, 1822, p. 201, pi. 23, fig. 66 (Gangetic estuaries). 



Macrones gulio von Maktens, 1876, p. 400 (Petchaburi) (identification doubt- 

 ful).— Hoka, 1923b, p. 171 (Menam Chao Phya at Nontaburi). 



Mystus gulio Fowlek, 1934a, p. 95 (Bangkok) ; 1934b, p. 337 (Krat) ; 1939, p. 44 

 (Krabi). 



A species of very wide distribution (India, Burma, Ceylon, Thai- 

 land, Malay Peninsula, Sumatra, Borneo, Java, Madoera), M. gulio 

 abounds in the lower courses of the tidal rivers discharging into the 

 Gulf of Siam, and doubtless occurs also on the western side of Penin- 

 sular Siam, although there are no definite records therefrom. 



The fish reaches great abundance in the rivers debouching into the 

 head of the Gulf of Siam, and has been collected also in the Patani 

 River and in the gulf at Pakpoon, Peninsular Thailand, and at Chanta- 

 bun and Krat, Southeastern Thailand. In the Menam Chao Phya 

 the fish regularly ascends as far as Pakret. Young fish, up to 6 to 7 

 cm. long, go in immense, compact schools. In the Tachin and the 



