270 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



When the genus Crossocheilus was established by van Hasselt in 

 1823, ohlongiis was the only species mentioned. The description was 

 very meager and not sufficient for identification. In 1842 Cuvier and 

 Valenciennes described Laheo ohlongus as a new species based on van 

 Hasselt's specimen in the Leiden Museimi, and declined to recognize the 

 genus Crossocheilus as distinct from Labeo. Giinther (1868, vol. 7, 

 p. 73) and Weber and de Beaufort ascribed tlie species to Cuvier and 

 Valenciennes but Bleeker credited it to van Hasselt. 



CROSSOCHEILUS TCHANGI Fowler 



CrossocheiDtjiis tchangi Fowlek, 1935a, p. 126, figs. 71, 72 (Srisawat). 



Known only from a specimen, 17.3 cm. long, from Srisawat, Central 

 Thailand, this fish resembles C. ohlongus but has a somewhat deeper 

 body, dissimilar mouth structure, and different coloration. 



CROSSOCHEILUS RETICULATUS Fowler 



Crossocheilus reticulatus Fowler, 1935a, p. 128, figs. 73, 74 (Khao Nam Poo). 



Described from two specimens, 7.0 and 6.6 cm. long, from Khao Nam 

 Poo, Central Thailand. The scales of the back and sides are dark- 

 edged, giving the general appearance of a network, and there is a 

 large black blotch at the base of the caudal fin. 



CROSSOCHEILUS REBA (Hamilton) 



Cyprinus reba Hamilton, 1822, pp. 280, 386 (Bengal, Behar). 

 Crossocheilus reba Guntheb, 1868, vol. 7, p. 74 (Siam). — Smith, 1931d, p. 186 

 (Sikuk River). 



This species, occurring throughout India, has been found to be very 

 abundant at times in Central Thailand. A noteworthy run in the 

 Sikuk River, Central Thailand, November 26-, 1923, consisted of 

 schools of young fish moving upstream, the schools often reaching 

 from the shores far out into the stream in a solid mass and along the 

 banks for several hundred yards in an unbroken body. 



The fishes were from 4 to 8 cm. long, a few of them 9.5 cm. 



A similar movement, involving young fishes of this and other 

 species, may be seen in the large rivers of Central Thailand every year. 

 The fishes, hatching in the minor streams that intersect the ricefields 

 during the rainy season, gradually drop down into the main rivers 

 and then, the rains having ceased and the flood waters having begun 

 to subside, they start upstream on a long migration which, in the 

 Menam Chao Phya, may carry them as far as Paknampo or farther 

 into the Meping and Menan, their numbers diminishing daily and only 

 a remnant of the original stock reach the upper waters. They are 

 preyed on by fish, birds, snakes, and monitor lizards, and have to run the 

 gauntlet of innumerable nets and traps set along the shores and oper- 



