FHESH-WATER FISHES OF SlAM, OR THAILAND 353 



The length attained in the Dutch East Indies is about half a meter. 

 In Thailand, the fish is reported to reach a larger size than the speci- 

 mens taken at Nong Khor and Hoopbon. 



The local vernacular name is pla duk lampan. 



PROPHAGORUS CATARACTUS (Fowler) 



Phagorus catai-actus FowMai, 1939, p. 54, figs. 1-3 (Trang). 



Described from a single specimen, 21 cm. long, from a waterfall 

 stream near Trang, this species appears to differ from P. nieuhofii 

 not so much in most of the characters cited by Fowler (length of 

 barbels, position of the dorsal fin, length of ventral fins, size of cau- 

 dal fin, and degree of spottiness, all of which might vary with age) 

 jis in the vomerine dentition and the number of dorsal and anal rays, 

 as well as in the relative depth of body. The dorsal rays number 67, 

 as against 87 to 106 in P. nieuhofii, the anal rays are 54, compared 

 with 69 to 95, and there is no backward median projection in the 

 band of vomerine teeth, which in P. nienhofii is a characteristic fea- 

 ture. The greatest depth of body is contained 6.5 times in the stand- 

 ard length, while in P. nieuhofii it is 8 to 9.3. 



Family PLOTOSIDAE 



Genus PLOTOSUS Lacepede 



Plotosus LiACEPi;DE, Histoire naturelle des poissons, vol. 5, p. 129, 1803. (Type, 

 Platystacus anguillaris Bloch.) 



These fishes are primarily marine but are often found in estuaries 

 and the mouths of rivers, and sometimes push well up into fresh water. 

 Of the four or five species known from southeastern Asia and the 

 Indo-Australian Archipelago, two are common in Thailand : 



la. Dorsal rays 80 to 100; anal rays 70 to 80; vomer with a crescentic band 

 of teeth, of which the mesial teeth are in 2 or 3 rows ; mandibular teeth 

 in 2 or 3 rows ; nasal barbel short, not reaching beyond eye ; gill rakers 

 on first arch 25 lineatus 



16. Dorsal rays 130 to 140; anal rays 105 to 120; vomer with a crescentic band of 

 teeth, of which the mesial teeth are in 4 rows ; mandibular teeth in 3 to 5 

 rows ; nasal barbel longer, reaching well behind eye or even to nape ; gill 

 rakers on first arch canius 



PLOTOSUS LINEATUS (Thunberg) 



Silurus lineatus Thunbekg, 1791, p. 190 (Indian Ocean). 



Plotosus anguillaris voN Martens, 1876, p. 399 (Bangkok). — VVebeb and de 



Beaufort, 1913, vol. 2, p. 229.— Smith, 1930, p. 54 (Siam).— Fowler, 1937, p. 



133 (Paknam Chao Phya). 

 Plotosus lineatus Smith, 1941a, pp. 15, 16 (revival of first available specific 



name). 



Of very wide distribution in the Pacific and Indian Oceans, and of 

 common occurrence in the Gulf of Siam, this species was not found in 



