236 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



9.6 to 11.5 cm. long, caught in the Nan Kiver on April 23, 1930, was 

 brought in by Luang Praserth Aksorn, then with the Siamese Bureau 

 of Fisheries. 



This is a comparatively small species, with a maximum length of 15 

 cm. among the specimens examined. The Deignan collection contains 

 28 specimens, 7.5 to 10.2 cm. long, from the Mechem, tributary of 

 the Meping, July 1 to 5, 1935. These were taken by A. R. Buchanan 

 and P. D. Harrisson, of Chiengmai. From the Menam Nan at Nan 

 on March 29, 1936, Deignan took six specimens 9.6 to 11.6 cm. long, 

 one of them 11 cm. long being a female with large eggs. A further 

 specimen 9.7 cm. long was from the Meta, a branch of the Mechem, 

 February 1936. 



Specimens taken in December have a marked development of pearl 

 organs on the top and sides of the head and on the back as far as the 

 dorsal fin; and females 9.6 cm. long with large ovaries are among 

 specimens collected in January. 



Vast schools of this species and other small cyprinoids begin to move 

 upstream in the large rivers after the end of the rainy season and 

 constitute one of the most outstanding phenomena of fish life in Cen- 

 tral Thailand. Such fish are called ;?/a soi by the Thai. 



Genus HOLOTYLOGNATHUS Fowler 



Holotylognathus Fowleb, Proc. Acad. Nat. Sei. Philadelphia, vol. 86, p. 135, 1934. 

 (Type, HolotylognatJms reticulatus Fowler.) 



The genus Holotylognathus, established for the accommodation of 

 H. reticulatus Fowler, has as its outstanding character the absence of 

 a lateral line ; otherwise there is general agreement with Tylognathus. 



HOLOTYLOGNATHUS RETICULATUS Fowler 



Holotylognathus reticulatus Fowler, 1934a, p. 135, figs. 97, 98 (Eastern and 

 Northern Siam). 



This species is represented by many specimens 3.4 to 8.3 cm. long. 

 The type and several other specimens came from Bua Yai, on the 

 Mekong in Eastern Thailand, and several hundred specimens came 

 from Chiengmai and the Metang in Northern Thailand. 



The single pair of small barbels are rostral. The broad lips are 

 fleshy, the upper plicate, the lower papillate. The fin formulae are 

 as in Tylognathus. The dorsal fin is situated well forward, its origin 

 in advance of ventrals and over the tip of the pectorals. The scales, 

 in very regular lengthwise and transverse rows, number 34 in lateral 

 series, 9 in cross series, and 9 predorsal. The coloration is plain 

 except for a large round black spot on the posterior part of the caudal 

 peduncle, and each scale of back and sides has a dark edge, forming 

 a reticulated pattern. 



