FRESH- WATER FISHES OF SIAM, OR THAILAND 471 



Chiengmai ; Hiiey Kao, a branch of the Meping ; Melong, a tributary of 

 the Mechem ; Meklang, on Doi Angka ; and Huey Mekong Kha, a trib- 

 utory of the Salwin at the foot of Doi Mekong Kha ; also Huey Nam 

 Puat, a tributary of the Mekong in French Laos, just over the border of 

 Nan Province. 



O. gachua is one of the smallest members of the genus, rarely exceed- 

 ing 20 cm., and in the restricted habitat of small mountain brooks it 

 reaches maturity when 10 cm. long. 



It displays the hardiness of its relatives and is an attractive little 

 creature. Although of dull coloration, the dorsal, caudal, anal, and 

 pectoral fins have a narrow, sharply defined blood-red margin (which 

 becomes white in alcoholic specimens and is referred to as white in some 

 of the published descriptions), and the pectorals are prettily marked 

 in many of the full-grown examples with a black spot at the base and 5 

 or 6 narrow, distinct, black cross bands (referred to by Day but not 

 by Weber and de Beaufort). 



The lateral line varies within narrow limits. It usually stops at the 

 eleventh to thirteenth perforated scale and resumes on the next scale 

 of the next row. Variations met with in a lot of specimens from a 

 tributary of the Meping in Northern Thailand were: (1) Lateral line 

 stopping at tenth scale on each side and resuming on the next scale 

 of the next row; (2) lateral line stopping at tenth scale on one side 

 and resuming at thirteenth scale of row below, and stopping at thir- 

 teenth scale on other side and resuming at fourteenth scale of row be- 

 low; (3) lateral line stopping at eleventh scale of one side and twelfth 

 scale of other side ; (4) lateral line stopping at eleventh scale of one 

 side and resuming at thirteenth scale of next row, and stopping at 

 thirteenth scale of other side and resuming at fourteenth scale of next 

 row; (5) lateral line stopping on thirteenth scale of one side and four- 

 teenth of other side, and resuming on next scale of row below. 



This fish is known in all parts of Thailand as pla hang. 



OPHICEPHALUS MELASOMUS Bleeker 



OphicepJialus melasoma Bleeker, 1851 (49), p. 424 (Sambas, Borneo). 

 Ophiocephalus melanosoma Bleekeb, 1865 (347), p. 34 (Siam) ; 1865 (356), p. 



174 (Siam).— Sauvage, 1881, p. 160 (Siam).— Webek and de Beaufort, 1922, 



vol. 4, p. 319 (Siam). 

 Channa melasoma Fowler, 1937, p. 224, fig. 215 (Mepoon, Kemarat). 



The range of this species extends from Indo-China through Thai- 

 land to Sumatra, Borneo, and Palawan. Definite localities for Thai- 

 land are those given by Fowler (1937) and headwaters of the Menam 

 Mun at Pakjong in the Eastern district. From the last-named place 

 numerous small specimens, taken May 12, 1925, exhibit the character- 

 istic coloration : Generally dark green or dark blue, with a bright red 

 band from snout to caudal fin. 



A maximum length of 30 cm. is attained. 



