FRESH-WATER FISHES OF SIAM, OR THAILAND 333 



section, seems to be its principal resort. On January 6, 1924, a speci- 

 men 75.5 cm. long was collected at Paknampo and a fish 88 cm., long 

 was examined there. A fishery conducted with seines in the deeper 

 parts of the river near Paknampo yielded five or six fishes daily in 

 December and January for the local market, and examples a meter 

 long and weighing 50 kg. have been taken there. Another fishing cen- 

 ter is the Lopburi River, whence fish are sent to the Bangkok market 

 during the season of high water. 



This fish is well known to the fishermen, who give it names borne 

 by no other species. One vernacular name is pla tuk (or ituh or itok)^ 

 perhaps in allusion to its somber color. Another is pla itub {ituh, to 

 beat), possibly in reference to the splash made by the fish when it 

 strikes the surface of the water after having leaped out in pursuit of 

 small cyprinoids. Still another name is pla khao dam {dam, black), 

 to distinguish it from Wallagonia attu, which is called pla khao {khao, 

 white). 



Genus PARASILURUS Bleeker 



Parasilurus Bleeker (299), Versl. Med. Akad. AnisterdaDi, vol. 14, pp. 392, 394, 

 1862. (Type, Silurus japonicus Schlegel.) 



PAKASILURUS COCHINCHINENSIS (Cuvier and Valenciennes) 



Silurus cochinchinensis Ctn'iER and Valenciennes, 1839, vol. 14, p. 352 (locality not 

 given). 



The inclusion of this species in the Thai fauna is based on a specimen, 

 22.6 cm. long, collected by Layang Gaddi on September 11, 1933, in a 

 waterfall stream on Kao Chong, near Trang, in Peninsular Thailand. 

 Features of this specimen are: Lower jaw slightly shorter than the 

 upper, vomerine teeth in a continuous transverse band, maxillary 

 barbels extending on the anal fin, mandibulary barbels reaching base 

 of pectorals, anal rays 63, ventral rays 9, pectoral rays I, 14, anal fin 

 united with the caudal, and lower caudal rays appreciably longer 

 than the upper. 



In the original description of this species from Cochinchina by 

 Cuvier and Valenciennes in 1839, the vomerine teeth were stated to be 

 divided into two groups; Day (1878, vol. 2, p. 481) gave these teeth 

 as "in two oval spots on the vomer divided by a smooth interspace" ; 

 and Giinther (1864, vol. 5, p. 34) referred to them as "forming a band, 

 which is a little interrupted in the middle." Examples from Hainan 

 Island, China, in the American Museum of Natural History, cour- 

 teously examined by John T. Nichols, curator of recent fishes in 

 that institution, were found by him to have the vomerine teeth either 

 in a continuous band, as in the Thailand example, or the band with a 

 median indentation posteriorly, but never were the teeth definitely 

 separated into two discontinuous patches. These variations in 



