30 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 79 



strong ossesous part weakly serrated on its posterior side and 0.4 

 total length of the ray ; dorsal branched rays becoming progressively 

 shorter, so that last ray is only 1.5 times diameter of eye and the 

 posterior border of fin is nearly vertical; dorsal base short, 2.5 in 

 head ; adipose fin small, its length less than base of dorsal, distance 

 between the fins 3 times length of base of dorsal ; caudal large, longer 

 than head, deeply forked, the lobes pointed ; anal rays iv, 26, longest 

 ray equal to postorbital part of head; base of fin 2.5 base of dorsal 

 and somewhat less than 0.25 standard length; first ray of ventrals 

 filamentous and reaching beyond middle of anal; pectoral spine 

 similar to dorsal spine as to size and serrations, its filamentous tip 

 as long as the spine and extending to anal. 



Color: Above slaty gray, below white; a roundish, glistening 

 white humeral spot twice diameter of eye ; dorsal, adipose, and caudal 

 fins black ; ventrals and pectorals blackish ; anal with dusky areas. 



Type. — The type specimen in the collection of the Siamese De- 

 partment of Fisheries was taken in the Menam Chao Phya at Koh 

 Yai, Central Siam, March, 1928. It is 61.6 cm. long. 



Remarks. — The principal differential characters of this species 

 are to be seen in the united band of vomero-palatine teeth, the short 

 barbels, the filamentous dorsal, ventral, and pectoral fins, the colora- 

 tion of the fins, the white humeral spot, and the colossal size. 



This fish is known along the Menam Chao Phya as pla tepa. 

 This name is to be distinguished from pla tepo^ applied to a common 

 fish of the same genus {Pangasius larnaudi) which differs markedly 

 in various respects, one striking feature being a large shiny-black 

 humeral spot. 



In point of size this fish rivals the celebrated Pangasius of the 

 Mekong basin called pJa huk by the Siamese. In former times fish 

 3 meters in length were sometimes taken, and at least one fish of 

 this size has been recorded within eight years. In recent years, 

 examples over 1.5 meters in length have been rare. 



The pla tepa frequents the entire length of the Menam Chao Phya, 

 but is nowhere abundant. Within a few years, fish reaching the 

 Bangkok markets have come mostly from the section of river below 

 Ayuthia, and the largest observed have been about 1 meter long. 



Named in honor of the late Dr. Yai S. Sanitwongse, in recogni- 

 tion of his keen personal interest in the fishes of Siam. It was he 

 who first brought this species to the writer's attention and pointed 

 out its distinctive characters. 



ARIUS SCIURUS, new species 



Description. — Body rather stout, moderately compressed, depth 

 slightly less than .25 length to base of caudal ; least depth of caudal 

 peduncle .5 postorbital part of head; head conical, its depth about 



