FRESH- WATER FISHES OF SIAM, OR THAILAND 415 



of the Menam Chao Phya, September 8, 1923, at a time when a great 

 volume of fresh water was entering the head of the gulf. A specimen 

 in the British Museum was collected by Flower in the Menam Chao 

 Phya. 



This species may be recognized easily by its very wide mouth, short, 

 broad head, edentulous palate, and three pairs of short barbels. 



A length of 25 cm. is reached, but the usual size of specimens col- 

 lected in Thailand is 12 to 15 cm. 



Vernacular names for the fish are pla uk hua hin, reported for the 

 Bangkok area, pla Jcot hua to, heard on the Bankpakong River, and 

 pla kot hieng. 



Genus HEMIPIMELODUS Bleeker 



Hemipimelodus Bt.kickeb (189), Act. Soc. Sci. Indo-Nederl, (Siluri), vol. 4, p. 236, 

 1858. (Type, Pimelodus torneensis Bleeker.) 



The hemipimelodids in Thailand are in general fishes of the lower 

 courses of the larger rivers. Of the five species ascribed to Thailand, 

 three are of somewhat doubtful status ; one, Hemipimelodus cochlearis 

 Fowler (1935a), is not a member of this genus, being excluded by the 

 presence of palatine teeth ; and only one {H. horneensis) is a common 

 and widely distributed fish, which occurs also in Borneo and Sumatra. 



It may now be announced, possibly for the first time, that H. hor- 

 neensis, and inferentially in other species of this genus, oral incuba- 

 tion is practiced as in Tachysurus and Osteogeneiosus. The eggs are 

 large and few in number, and as extruded they are taken into the mouth 

 of the male, where they are held during hatching and the absorption of 

 the yolk sac. Ovigerous females develop a large pad on the inner side 

 of the last ventral rays, the pair of pads serving to hold each egg as 

 extruded until it can be fertilized and taken into the male's mouth. 



The following characters will differentiate the species of Hemipi- 

 Tnelodu^ inhabiting Thailand : 



la. Eyes subcutaneous ; length of head 4 to 4.5 in standard length ; gill rakers on 

 lower arm of first arch 10; anal rays 18 to 20 borneensis 



16. Eyes with a free cutaneous rim; length of head 3.25 in standard length; gill 

 rakers on lower arm of first arch about 12 ; anal rays 15 velutinus 



Ic. Differential characters not known ; anal rays 16 siamensis 



HEMIPIMELODUS BORNEENSIS (BlecKer) 

 FiGITKE 93 



Pimelodus dorneensis Bleekee, 1851 (49), p. 430 (Sambas, Borneo). 

 Hemipimelodus lorjieensis Bleekee, 1865 (347), p. 34 (Siam]^; 1865 (356), p. 175 



(Siam). — ^VON Martens, 1876, p. 400 (Bangkok). — Weber and de Be^vufort. 



1913, vol. 2, p. 327 (Siam).— Hoea, 1923b, p. 170 (Nontaburi).— Fowler, 1935a, 



p. 101, fig. 24 (Bangkok). 



This species has been found along the entire length of the Menam 

 Chao Phya and in some of its connecting streams. It has been col- 



