FRESH-WATER FISHES OF SIAM, OR THAILAND 413 



Almost everywhere on the Thailand coasts the fish has a name, 'pla 

 tukang, which is given to no other species. This designation may be 

 derived from pedukang and helukufng^ Malay names for the fish. 



TACHYSURUS SAGOR (Hamilton) 



Pimelodus sagor Hamilton, 1822, p. 169 (Ganges). 



Many specimens of this broad-headed fish, with large subcircular 

 occipital process and with conspicuously granulated top of head and 

 humeral processes, have been taken on both sides of the Gulf of Siam, 

 in the sea, in the estuaries, and in the short tidal rivers. Besides the 

 Dutch East Indies, the species is known from the Straits Settlements 

 and India. 



It reaches a length of 45 cm. 



The striking palatine teeth masses, usually in 4 transverse patches, 

 are subject to some variation. An aberrant arrangement in a speci- 

 men, 35 cm. long, taken from Bandon Bight September 29, 1923, was 

 an undivided lenticular patch separated from its fellow by a space 

 wider than the diameter of the eye. 



The fish in life usually shows silvery white or bluish green cross 

 bands on back and sides. 



Oral incubation reaches a climax in this species. A male fish, 35 

 cm. long to the tip of the caudal lobes, taken on October 20, 1923, 

 at Pakpoon, on the west side of the Gulf of Siam, had in his mouth 

 48 eggs measuring 1.1 to 1.2 cm. in diameter. Another fish caught at 

 the same time had in his mouth an agglutinated mass of eggs, 39 in 

 number, resembling a bunch of grapes. In the posterior part of the 

 pharynx, behind the eggs, were 4 hatched fish 4 cm. long. Obviously 

 this male had taken in a fresh batch of eggs before all the young of the 

 previous batch had been able to leave the mouth. 



TACHYSURUS STORMII (Bleeker) 



Cephalocassis siormii Bleekh3i, 1858 (lS9a), p. 246 (Sumatra). 



This is apparently a rare species in Thailand waters. Only a single 

 specimen is referable to it, this an ovigerous female, 40 cm. long, taken 

 in the Menam Chao Phya above Bangkok, on April 30, 1928. The 

 species is recorded from Sumatra and Borneo. 



TACHYSURUS THALASSINUS (Ruppell) 



Bagrus thalassinus RuppeJll, 1835-1840, p. 75, pi. 20, fig. 2 (Massaiia, Abyssinia). 

 As its name implies, this is a marine species, apparently rarely 

 entering streams but often approaching their mouths. To the many 

 localities from which this form has been reported (Australia, New 

 Caledonia, Red Sea, Zanzibar, Philippines, and East Indian islands) 

 it is possible to add the Gulf of Siam and Puket, a Thailand island 

 in the Bay of Bengal. 



