60 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



Central Thailand, December 11, 1924, the lengths were : One, 24 cm., 

 one, 26 cm., four, 28 cm., one, 29 cm., two, 33 cm., one, 34 cm., one, 35 

 cm., and one, 38 cm. 



In life the adult fish has a nearly uniform silvery gray or light 

 bronze or copper color. Young fishes are marked with narrow dark 

 gray or blackish cross bands of somewhat irregular shape, mostly 

 wider than the interspaces. The bands, numbering 25 to 30, begin on 

 the nape and extend to the base of the caudal fin. The 4 or 5 anterior 

 ones extend from the back across the opercle and are approximately 

 vertical; the others are inclined downward and forward. The bands 

 begin to disappear when the fish are about 10 cm. long, and at a length 

 of 15 cm. only vestiges remain. Occasionally traces of the transverse 

 bands persist, especially anteriorly, in nearly full-grown fishes. 



Insects, crustaceans, and succulent roots of aquatic plants constitute 

 the principal food of this species. 



At the period of flood water, the adults enter the swamps and deposit 

 eggs on submerged roots of aquatic plants. Observations on egg-lay- 

 ing, incubation, growth, and behavior of young are much less extensive 

 than for A^. chitala. With the subsiding of the flood waters, the adult 

 and young leave the swamps and enter the rivers and canals in great 

 numbers. 



The flesh is sweet but full of small bones. Large quantities are 

 caught for domestic consumption and for sale, and in some places 

 there is at times an active special fishery. In some of the canals extend- 

 ing eastward from the Menam Chao Phya to the Menam Bangpakong, 

 hundreds of large scoop nets (Yokyaw) are operated. The fishes are 

 eaten either fresh or smoked. Their shape adapts them for smoking 

 whole, and after that treatment they are distributed over all parts of 

 the country. 



The Siamese name for this fish is pla chalat or pla salaf, meaning 

 clever or cunning fish. 



Order Opisthomi 



Family MASTOCEMBELIDAE: Spiny Eels 



The mastocembelids are acanthopterygian fishes of extraordinary 

 aspect, eellike in shape, with minute scales, a pointed snout terminat- 

 ing in a movable fleshy tip, small mouth, minute jaw teeth, small 

 gill openings on the under side of the head, anterior nostrils widely 

 separated from the posterior and contained in a tentacle on the side 

 of the rostral appendage, very long dorsal and anal fins composed 

 partly of strong, short spines, and deficient ventral fins. They re- 

 semble the true eels in having the shoulder girdle not suspended from 

 the skull. Authorities have differed as to their systematic position. 



