Fish of the Tale Sa]). 
475 
Mastacembelus argus ((Tiinth ). 
iS6i. Mdsliiceiiibelus argus, Giiiither Cat. Brit. Mus. Fish. III. ]>. 542. 
A single specimen of this species was caught by Dr. Annaudale near the 
mouth of the Patelung river. Dr. Annandale tells me that when fresh the speci- 
men was very dark olive green, almost black, with blood red markings. 
Mastacembelus argus is endemic in Siam. 
Mastacembelus circumcinctus, sp. nov. 
The new species is represented by a single specimen obtained by Dr. Annandale 
near the mouth of the Patelung river in the inner portion of the Tale Sap. 
The specimen is quite young and is only 135 mm. in total length without the 
caudal and the fleshy appendage. 
The length of the head is contained 6 2 times and the greatest depth of the 
body 6-6 times in the total length without the caudal. The snout is naked and 
is contained about 2 6 times in the length of the head. The eyes are situated wholly 
in the anterior half of the head. There is a well-marked preorbital spine and there 
are three preopercular spines. The lowermost is very small and is closely adnate 
to the base of the second, the third is the largest. The mouth is small and its 
opening does not extend to below the nostrils. The anus is provided with a 
well-marked papilla and is situated considerably nearer the base of the caudal 
than to the tip of the snout. 
Text-fig. ^.—Lateral view of Mastacembelus circumcinctus sp. nov. (slightly reduced, 
spines dissected out). 
The dorsal fin commences above the last third of the pectoral and contains 
29 spines which increase in length from before backwards except the last one which 
is much shorter than the one preceding it and is almost buried in the skin. The 
dorsal fin possesses 46 soft rays. The anal fin begins below the 25th spine 
of the dorsal and contains three spines and about 56 .soft rays. The second 
spine is the largest. The vertical fins and the caudal are all continuous. The 
pectoral is quite small and is about one-third the length of the head. 
The colour of the species in spirit is very characteristic. It is brownish on 
the upper surface and the sides and yellowish beneath. The head and body 
are marked with very characteristic dark brown bands encircling the fish. They 
are broader above and become narrower on the sides and the under surface. They 
end in a row of black spots along the base of the dorsal and are continued as 
short bands on the anal A white streak runs on either side from behind the 
