FRESH-WATER fishes of SlAM, OR THAILAND 221 



History. From the first -named species a difference of cardinal impor- 

 tance is in the number of branched dorsal rays (16 to 18 in A. a-smussi^ 

 11 or 12 in A. deignani). Although Dybowski credited no barbels to 

 his form, specimens in the National Museum otherwise agreeing very 

 closely with A. asm/ussi and coming from the same waters as Dybow- 

 ski's material have a small but distinct maxillary barbel. Similarly, 

 A. guichenoti has 16 to 18 branched dorsal rays and other points of 

 difference. 



Of the various species of Acanthorhodeus recorded from Indo- 

 china and Siberia, the present form appears to be closest to Vaillant's 

 imperfectly described species A. tonkmensis from the river Noi in 

 upper Tonkin, which is known also from Hainan. In that form, how- 

 ever, the dorsal rays were given as iii, 15 ; and in a specimen about 8.9 

 cm. long from Hainan the branched dorsal rays number 15, although 

 Nichols and Pope (1927) give the rays as 13 to 15 specimens from that 

 island. Other differences shown by the Chinese form are the dorsal 

 profile more arched than the ventral, the nuchal concavity, and the 

 extension of the ventral fins on the anal. 



Named for H. G. Deignan, who collected these first representatives 

 of the genus Acanthorhodeus found west of the Mekong. 



Genus LABIOBARBUS van Hasselt 



Labiobarbus van Hasselt, Alg. Konst. Letterbode, vol. 2, p. 132, 1823. (Type, 

 Labiobarbus leptocheilus van Hasselt.) 



The fishes of this genus have for about a hundred years been re- 

 ferred to the genus Dangilu Cuvier and Valenciennes (1842). An 

 earlier name, Lahioharbus^ which has been generally overlooked or 

 ignored, was given by van Hasselt in 1823, with two Javan species^ 

 leptocheilus and Upocheihis, mentioned thereunder. These two names, 

 adopted by Cuvier and Valenciennes, are acknowledged to be those of 

 van Hasselt. The genotype of Dangila was fixed by Bleeker in 1863 

 as leptocheilus. The generic name Labeoharbus of Riippell (1836), 

 which has usually been applied to cyprinoid fishes of an entirely dif- 

 ferent kind, was thus a synonym of Labiobarbus van Hasselt and was 

 otherwise unavailable, having been antedated by Tor of Gray. 



These fishes are common in the rivers of Thailand and are recognized 

 easily as to genus by the extremely long dorsal fin, which in local 

 species has from 21 to 27 branched rays, combined with fringed upper 

 lip, lips continuous at the corners of the mouth, sharp edge of the lower 

 jaw, well-developed rostral and maxillary barbels, and small scales. 

 Some of the species are very similar to each other, and are separated 

 by a combination of minor features rather than by outstanding single 

 characters. 



A length of 30 cm. is rarely exceeded. 



