368 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



a unique color feature. The vomero-palatine teeth are in 4 separate 

 rounded patches forming an arch or crescent ; the gill rakers are numer- 

 ous (about 40 on the first arch) ; both the maxillary and mandibulary 

 barbels are well developed, longer than the head, and the maxillary 

 extend to the middle of the pectoral fins or to the ventrals ; the branched 

 anal rays number 29 to 30; and there is on the opercle a large rounded 

 dark blotch. 



PANGASIUS MACKONEMUS Bleeker 



Pangasius macronema Bleeker, 1851 (26), p. 11 (Bandjermassing, Borneo) ; 1865 

 (347), p. 34 (Siam) : 1865 (356), p. 175 (Siam).— Sauvage, 1881, p. 162 (Slum, 

 Grand Lakes of Cambodia ) . — Foavler, 1935a, p. 98, fig. 17 ( Bangkok ) . 



The known range in Thailand covers the Menam Chao from below 

 Bangkok to Palniampo, the Menam Sak below the barrage at Dha 

 Luang, the Menam Lopburi at Lopburi, and the lower Menam Nan. 

 A specimen obtained by Deignan from a fisherman in the gorge of 

 the Meping on December 24, 1935, is interesting as being one of the 

 very few fishes known from the Meping rapids. Several specimens in 

 the British Museum were gifts from the Siamese Museum many years 

 ago. 



In Thailand this is a rather small species. The largest specimens 

 have been 21.5 cm. long. 



Local vernacular names borne by this species are pla sangkoAJoad 

 and pla ai dong^ used by fishermen on the Pasak River. 



PANGASIUS SIAMENSIS Steindachner 



Pangasius siamcnsis Steindachner, 1879, p. 393 (Menam Chao Phya at Bang- 

 kok ) .—Sauvage, 1881, p. 162 (Siam) ; lS83b, p. 154 (Menam Cliao Pliya).— 

 HoRA, 1923b, p. 167 (Bangkok).— Fowler, 1934a, p. 88 (Bangkok) ; 1935a, p. 

 98, fig. 16 (Bangkok) ; 1937, p. 138 (Bangkok, Mepoon). 



This species is apparently peculiar to the basin of the Menam Chao 

 Phya in Thailand. It was described by Steindachner from a specimen 

 25 to 26 cm. long from the Menam Chao Phya. Hora (1923b) had two 

 young specimens from Bangkok. Fowler (1934a, 1935, 1937) reported 

 numerous specimens from Bangkok and one from Mepoon. Specimens 

 were collected by the writer at Paknam, near the mouth of the Menam 

 Chao Phya ; at Pakret on the same river above Bangkok ; and in the 

 Pasak at the irrigation barrage at Dha Luang. 



The relations of this species are closest to P. macroncmus, as indi- 

 cated in the key. Steindachner wrote : 



In the length of the maxillary barbels this species is nearest to Pangasius macro- 

 nema (from Siam, Borneo, and Java), in the form of the four patches of palatine 

 teeth to Pang, micronema Blkr., in the size of eyes and the shape of the head to 

 Pang, tios Blkr. But in my opinion it is not very probable that on examination of 

 a larger number of specimens the identity of P. siamcnsis with P. macronema 

 would be found. 



