338 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



Menam Lopburi at Lopburi ; Menam Chao diet at Ban Poll ; Menam 

 Nan basin at Bung Borapet and Klong Borapet) ; Southeastern Thai- 

 land (Menam Chantabun at Chantabun and Kao Sabap; Klong Ban 

 Taeng, Krat) ; Peninsular Thailand (Tale Sap; Tale Noi; Klong 

 Kae Chieg at Patalung; Klong Nakon Noi at Nakon Sritamarat; Pa- 

 tani Kiver at Patani) ; Eastern Thailand (tributaries of Menam Mun 

 at Korat) . 



This fish attains a length of 40 to 45 cm., but the usual size of fish 

 caught in Thailand does not greatly exceed 25 cm., and many only 

 15 to 20 cm. long are seen in the markets. 



Two females, 25.5 cm. long, taken October 8, 1923, in the Tale Noi 

 had large ovaries with nearly ripe eggs ; another of similar size caught 

 October 15, 1923, with a cast net in the Patani River at Patani also 

 had large ovaries. 



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Figure 77. — Ompok bimaculatus (Bloch). Drawn by Luang Masya; courtesy of the 



Thailand Government. 



The fish in Thailand is subject to considerable variation in body 

 proportions, and similar characters which, in some cases, may justify 

 recognition as races or subspecies. Specimens from Peninsular Siani 

 and from the Pasak, Lopburi, and Chao Cliet Rivers in Central Siam 

 have been set aside tentatively as representing new forms, but final 

 action should await more material that may indicate the range of 

 normal variation in the species. Hora (1936b) has shown that a 

 dozen or more nominal Indian species of Om'poh described by Hamil- 

 ton, Day, and others may be safely assigned to Mmaculatus. 



This fish bears a variety of names, some peculiar to it, some shared 

 by related species. A common name of wide use is pla nua on (soft- 

 flesh fish). Another, employed in both Peninsular Siam and South- 

 eastern Thailand, is pla cha oan. In the Tale Noi this name is 

 shortened to pla oan (bent fish). At Paknampo, at the head of the 

 Menam Chao Phya, the name pla na san (short-snout fish) may be 

 heard. Among Malay fishermen in the Patani Province a name in use 

 is ikan laeh itam. 



