FRESH-WATER FISHES OF SIAM, OR THAILAND 377 



2b. Gill membranes almost totally separated from each other and from the 

 isthmus ; vomerine teeth in a curved band ; dorsal spine vi'ith its posterior 



side smooth or with teeth directed dovpnward Leiocassis 



Ih. Eyes not subcutaneous ; gill membranes free from isthmus and for most part 



from each other ; vomerine teeth in a curved continuous band. 



3a. Dorsal fin of moderate height, its spine serrated on its posterior side_Mystus 



3b. Dorsal fin very high, its spine long, slender, and unserrated on its posterior 



side Heterobagrus 



Genus BAGROIDES Bleeker 



Bagroides Bleekee (45), Nat. Tijdschr. Nederl-Indie, vol. 2, p. 204, 1851. (Type, 

 Bagroides melapterus Bleeker.) 



In Thailand these medium-sized river fishes are of very restricted 

 range and are uncommon or rare. They may be rather easily recog- 

 nized by their small head, conical snout, small mouth, long adipose 

 fin, short pectoral fin with a strong serrated spine, and striking colora- 

 tion: Yellow or brown ground color with large black blotches or 

 cross bands on head and body. 



The characters that separate the species are as follows : 



la. Vomerine teeth in single roundish patch; adipose fin free behind, its base 

 1 to 1.5 times length of bead ; dorsal, anal, ventral, and pectoral fins 



black distally melapterus 



16. Vomerine teeth in a single semilunar patch ; adipose fin with no free pos- 

 terior edge, its base twice length of head or longer. 

 2a. Dorsal and pectoral spines about length of head ; width of mouth about 

 equal to diameter of eye; dorsal, anal, ventral, and pectoral fins con- 

 spicuously blackish distally macropterus 



2&. Dorsal spine much longer than head and much longer than pectoral spines ; 

 width of mouth less than twice diameter of eye ; dorsal, anal, ventral, and 

 pectoral fins usually brown, sometimes blackish distally macracanthus 



BAGROIDES MELAPTERUS Bleeker 



Bagroides melapterus Bleekee, 1851 (45), p. 204 (Bandjermassing, Borneo). — 



Webee and de Beaufoet, 1913, vol. 2, p. 348 (Siam). 

 Bagroides melanopterus Saitvaqe, lS83b, p. 154 (Menam Chao Phya). 



No one but Sauvage has reported directly on the occurrence of this 

 species in Thailand. He listed it merely as among species repre- 

 sented in a collection obtained in the Menam Nan by Dr. Harmand. 

 The reference of Weber and de Beaufort is probably based on Sauv- 

 age's record. The fish, reaching a length of 34 cm., is otherwise 

 known only from Sumatra and Borneo. 



BAGROIDES MACROPTERUS Bleeker 



Bagroides macropterus Bleekee, 1853 (80), p. 515 (Moara, Sumatra). — Sauvage, 

 18S1, p. 161 (Siam and Sumatra) ; 1883b, p. 154 (Menam Nan). — Webee and 

 DE Beaufoet, 1913, vol. 2, p. 349 ( Siam) . 



Pseudohugrichthys mao-opterus Bleekee, 1865 (347), p. 34 (Siam) ; 1865 (356) 

 p. 175 (Siam). 



Observations thus far made indicate that in Thailand this fish has 

 occurred in recent years only in the lower Menam Chao Phya, the 



