FRESH-WATER FISHES OF SIAM, OR THAILAND 477 



Genus NEOSTETHUS Regan 



Neostethus Regan, Proc. Zool. Soc. London, 1916, p. 2. (Type, Neo.^tethus lankes- 

 teri Regan.) 



NEOSTETHUS SIAMENSIS Myers 

 Neostethus siamcrtsis Myers. 1937, p. 139 (Cliantabun Estuary). 



The type and only known specimen of this species, a female 2.87 cm. 

 in standard length, 3.6 cm. in total length, was collected by the writer 

 in April 1933 in the estuary of the Chantabun River, Southeastern 

 Thailand, The fish may be looked for in the lower reaches of the 

 river as well as where the large volume of fresh water from the river 

 mixes with the brackish water of the estuary, and it is very desirable 

 that additional specimens, especially males, be obtained so that Dr. 

 Myers or some other competent student of this group may determine 

 the exact relations of the species. 



Family POLYNEMIDAE: Threadfins 



Genus POLYNEMUS Linnaeus 



Polynemus Linnaeus, Systema naturae, ed. 10, p. 317, 1758. (Type, Polynemus 

 paradiseus Linnaeus.) 



Numerous members of the family of threadfins are found on the 

 coasts of Thailand, but only one species can be given a fresh-water 

 habitat. A ready means of recognition of the threadfins is the divi- 

 sion of the pectoral fins into two parts, the upper composed of normal 

 rays, the lower consisting of free filaments, which may be moved inde- 

 pendently and are tactile organs ; the number of filaments varies with 

 the different species (3 or 4, 5, 6, 7, and 14). All the polynemids are 

 considered good as human food, and some of the larger forms ( genus 

 Eleutheronema) , attaining a length of 2 meters, are of great commer- 

 cial importance in the salt and brackish waters. 



The general vernacular name is pla kurao. 



POLYNEMUS PARADISEUS Linnaeus 



Polynemus paradiseus Linnaeus, 1758, p. 317 (India). — von Martens, 1876, p. 

 390 (Menam Chao Phya at Paklat).— Hoea, 1923b, p. 177 (Nontaburi, Bang- 

 kok). 



This species of the coastal waters of India, Burma, Thailand, and 

 Malaya regularly enters fresh-water streams during the spawning sea- 

 son and probably at other times. Locally it is sometimes found in great 

 abundance as far up the Menam Chao Phya as Koh Yai, about 40 

 kilometers above Bangkok, and ascends also the Bangpakong and 

 other large streams debouching into the Gulf of Siam. 



