64 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



British Museum contains specimens from Thailand in the Mouhot and 

 Schomburgk collections ; also specimens from the upper Bangpakong 

 Kiver from the Siamese Museum and from the Menam Chao Phya at 

 Bangkok from Capt. Stanley Flower. In Thailand it is the common- 

 est, most widely distributed, and largest member of the genus. It is 

 found in rivers, canals, swamps, and lakes. 



A length of at least 70 cm. is attained in some Thai waters. A speci- 

 men, 25.5 cm. long, taken from the Menam Chao Phya at Koh Yai, 

 between Bangkok and Ayuthia, had no preorbital spine but was 

 otherwise typical. 



This species, and doubtless others of the genus, subsist on insects, 

 crustaceans, and small fishes. 



On account of its shape, slippery skin, powerful muscles, and activity 

 it is difficult to handle, and its short, sharp, stout spines can inflict 

 painful wounds. It is exposed for sale regularly in the markets and 

 it has some use as food. 



Everywhere in Thailand it bears the vernacular name of pla kath- 

 ing. 



MASTOCEMBELUS ARMATUS FAVUS Hora 



Mastacembelus armatus var. favus Hora, 1923b, p. 180 (Nontaburi) ; 1924a, p. 



474, fig. 2 (Tale Sap).— Fowler, 1934a, p. 146 (Chiengmai, Bua Yai). 

 Mastacembelus favus Fowxer, 1937, p. 222, figs. 204-209 (Mepoon, Bangkok). 



This fish is peculiar to Thailand, as far as present information 

 goes, and it is found at such widely separated places as the Tale Sap 

 in Peninsular Thailand and the upper waters of the Mechem, tribu^ 

 tary of the Meping, in Northern Thailand. 



A length of 40 cm. is attained by specimens in hand, but a length of 

 60 cm. is reported by fishermen. 



No structural characters have been pointed out by which M. a. favus 

 may be distinguished from armatus proper, but as a color variety it is 

 well defined. Five specimens, 3.8 to 5 cm. long, collected by Deignan 

 on April 22, 1935, in the Meping at Chiengmai have the body colora- 

 tion much subdued and the outstanding markings are a row of dark 

 brown spots at the base of the dorsal and anal fins, which are other- 

 wise white. Fowler (1937) has given six excellent figures showing 

 color variation. 



MASTOCEMBELUS ARGUS Gunther 



Mastacembelus argus GiJNTHEa;, 1861, vol. 3, p. 542 (fresh waters of Siara) ; 

 1864, p. 179 (Siam and Cambodia).— Peters, 1868, p. 263 (Slam).- von 

 Martens, 1876, p. 396, pi. 10, fig. 4 (Bangkok and Petchaburi ) .—Gunther, 



1880, p. 499, fig. 228 (illustration of a specimen "from Siam").— Sauvage, 



1881, p. 160 (Siam) ; lS83b, p. 151 (Menam Chao Phya ) .— Boulenger, 1912, 

 p. 201 (Siam).— HoEA, 1924a, p. 475 (Tale Sap).— Fowlee, 1935a, p. 134, 

 figs. 93^96 (Bangkok) ; 1939, p. 47 (Krabi). 



