FRESH- WATER FISHES OF SlAM, OR THAILAND 129 



In 1931 (Smith, 1931d, p. 185), from an examination of Day's de- 

 scription and figure, the writer expressed the opinion that "no char- 

 acters are ascribed to Matsya by Day that are not possessed by 

 Mystacoleucus^ and it is altogether probable that the two are identical." 

 The principal difficulty in recognizing Matsya as a synonym of 

 Mystacoleucus arose from the assumption by Indian ichthyologists 

 that Matsya argentea possessed only 5 branched rays in the anal fin, 

 an assumption that Day's figure did not seem to justify, and which 

 was later shown to be incorrect. 



Under the caption Mystacoleucus argenteus^ the writer (1933a) 

 published a note on numerous specimens that he obtained in December 

 1932, and January and February 1933, in the Salwin at Ta Ta Fang, 

 Thailand, and in five branches of the Salwin in Thailand and Burma; 

 following the original defect in the description and figure, these speci- 

 mens were incorrectly referred to as having no barbels, whereas they 

 show two well-developed pairs of barbels. 



The most recent contribution to the taxonomy of this species is a 

 detailed paper by Dr. Hora (1939) , in which he reconsiders his former 

 (1937e) view that Matsya is a genus distinct from Mystacoleucus. In 

 view of his statement (1939, p. 402) that "besides Day and the writer, 

 Vinciguerra is the only ichthyologist who has commented on the 

 systematic position of Matsya argentea^'' it may be assumed that Dr. 

 Hora overlooked the preceding citations, which were supplemented 

 by a number of letters indicating that Matsya is not a tenable genus. 



MYSTACOLEUCUS ATRIDORSALIS Fowler 



Mystacoleucus atridorsulis Fowler, 1937, p. 176, figs. 112, 113 (Kemarat). 



This species is known from two specimens, 6.6 and 6.7 cm. long, 

 from the Mekong at Kemarat, Eastern Thailand. It has no barbels 

 and is distinguishable by a large jet-black area on the distal part of 

 the dorsal fin. 



MYSTACOLEUCUS CHILOPTERUS Fowler 



Mystacoleucus chilopterus Fowleb, 1935a, p. 112, fig. 40 (Si'isawat) ; 1937, p. 176 



( Mepoon ) . 



Originally described from three specimens, 9.5 to 10.4 cm. long, from 

 Srisawat, Central Thailand, this fish was later noted by Fowler from 

 Mepoon, Central Thailand. Two specimens, 12 cm. long, from the 

 Mekok at Chiengrai were taken by the writer on March 2, 1924. 



The species is very close to M. marginatus, differing apparently in 

 fewer predorsal scales and body coloration. The free margins of the 

 dorsal and caudal fins have a sharply defined narrow black edge, as in 

 M. marginatus, and each caudal lobe has a dark submarginal longi- 

 tudinal streak. 



