FRESH-WATER FISHES OF SIAM, OR THAILAND 131 



The usual shape of the anal fin is truncate, as stated by Weber and 

 de Beaufort (1916, vol. 3) . There is, however, considerable variation. 

 Thus, a female, 14.2 cm. long, from the Menam Nan, has the free mar- 

 gin of the anal fin strongly convex, while a male 10.5 cm. taken at the 

 same place and time has a markedly emarginate anal. 



The occurrence of this species in lower Burma (Tenasserim) was re- 

 ported by Mukerji (1932, p. 285). The single specimen available, 7.5 

 cm. long, from the Kyenchaung River in the Mergui district, was fig- 

 ured and was said to "agree in all essential details" with the description 

 of Mystacoleucus marginatus given by Weber and de Beaufort; but 

 the figure shows only 7 branched rays in the dorsal fin and 7 

 branched anal rays, numbers that are excluded from the definition of 

 the genus as stated by Weber and de Beaufort. Mukerji compared 

 the Burmese fish with a specimen of M. margmatus collected by the 

 writer in Peninsular Thailand, and noted that whereas in the form^er 

 specimen the procumbent predorsal spine perforates the first predorsal 

 scale, in the Thailand example the spine perforates the third pre- 

 dorsal scale. The identity of the Burmese fish must be regarded as 

 unsettled. Inasmuch as M. marginatus is otherwise unknown from 

 Burma, and the place of capture of this particular specimen is in- 

 cluded within "the interior of Tenasserim" where Tickell reported 

 Acanthonotus argenteus as very common, the possibility that Mukerji's 

 specimen represents M. argenteus is to be considered, and a reexamina- 

 tion and full description are desirable. 



Vernacular names borne by this species in different parts of Thai- 

 land are distinctive. Throughout the Peninsula the fish is called 

 2}la ya. In the valley of the Nan River the name pla nam hi is in gen- 

 eral use. Along the Meping and its branches the usual vernacular 

 designation is pla hiyoh^ which is heard also on the Mekok at 

 Chiengrai. 



Genus COSMOCHILUS Sauvage 



Cosmochilus Sauvage Bull. Soc. Philom. Paris, sev, 7, vol. 2, p. 240, 1878. (Type, 

 Cosmochilus harmandi Sauvage.) 



COSMOCHILUS HARMANDI Sauvage 



Cosmochilus harmandi Sauvage, 1878b, p. 240 (Laos, Indo-China). — Hora, 1923b, 

 p. 158 (Bangkok).— FowLKB, 1935a, p. 120, figs. 58, 59 (Bangkok) ; 1937, p. 

 183, figs. 149, 150 (Bangkok). 



Described from Indo-China in 1878, this species has been found 

 to be not rare in the lower courses of the Menam Chao Phya and some 

 of the connecting streams. It is commonest in the stretch of river 

 between Ayuthia and Bangkok, and many examples therefrom caught 

 with cast net, seine, or pongpang have been preserved. At Pakret 

 on December 24, 1924, the use of cast nets indicated that this was one 



