284 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



late of 230 to 240 per minute, as evidenced by the pulsations of the 

 opercular flaps. A favorite resting attitude for the fish was with the 

 head projecting over a stone with the body supported by the pectoral 

 fins. At intervals all respiratory movements were suspended for a 

 period of 6 to 10 seconds. 



Protracted observation of the fish in aquaria in Thailand failed 

 to indicate normal breathing as in other fishes, the taking of water 

 through the mouth and passing it out over the gills. The ability to 

 breathe like ordinary fishes seems to have been entirely lost. 



Although the fish possesses a swim bladder, this organ, as in vari- 

 ous other mountain-stream fishes of the Orient, is very small and is 

 inadequate to function hydrostatically. The fish is unable to main- 

 tain itself off the bottom except by active swimming efforts. 



Radial flanges are highly developed on the dorsal and anal fins 

 of all adult examples. Their purpose is suggested in an introductory 

 chapter (page 32). 



The young are strikingly marked. In examples 4.6 to 5.5 cm. long 

 taken in Bung Borapet in August there is a brown band extending 

 along the lateral line from the base of the caudal fin to the head, 

 through the eye, to the tip of the snout, and from this band there 

 extend upward and downward about 11 short brown bars or spots 

 into the brownish yellow of the back and the creamy yellow of the 

 side. In specimens 6.9 to 7.7 cm. long collected in Bung Borapet in 

 November, the two series of brown spots along the side have become 

 more distinct, and about 11 dark brown blotches appear on the back. 

 The caudal fin shows irregular cross lines of brown spots. In fishes 

 from about 8 to 8.5 cm. long the longitudinal brown band disappears, 

 and each scale may have a well-defined brown spot at its base. With 

 further growth of the fishes into adult size, the brown spots on side 

 and back may be obscured or completely obliterated, as the general 

 coloration of the fish becomes dark brown or almost black in some 

 examples. 



Rostral tubercles begin to appear in fishes about 10 cm. long, and 

 by the time full sexual maturity is reached the tubercles form a con- 

 spicuous outgrowth on the snout. They are present in both sexes 

 but are much more developed in the male and take the form of stout 

 conical horny spines occupying pores, arranged in definite groups: 

 A. transverse band on the front of the snout; a broad median band 

 separated from the transverse band by a deep groove, and extending 

 to and behind the nostrils; and two or three small lateral groups in 

 advance of the nostrils separated on each side from the median band 

 by a groove, which is continuous with the cross groove. 



The fish regularly attains a length in excess of 20 cm., and maturity 

 is reached at 12 to 15 cm. The largest specimen obtained, 27.5 cm. 

 long, was taken in the Mekhan, Northern Thailand, February 8, 1932. 



