234 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



The species of TylogtiathtM may be differentiated as follows : 



la. No barbels ; scales in lateral line 27 ; coloration mostly pale brown above ; 

 silvery white below, small examples with a dark spot at caudal 



base brunneus 



1&. A pair of maxillary barbels ; scales in lateral line 32 to 36 ; coloration various. 



2a. Circumpeduncular scales 16; scales in transverse series to base of ventral 



fin 6-1-4; gill rakers about 8+25; a faint median longitudinal dark 



stripe deficient anteriorly, most distinct on caudal peduncle, where there 



is a round black spot about size of pupil; dorsal fin with no sharply 



defined dark edge caudimaculatus 



2&. Circumpeduncular scales 18: scales in transverse series to base of ventral 

 fin 6-1-5; gill rakers about 6+30; a round dark spot about size of eye on 

 caudal peduncle; dorsal fin with a narrow sharply defined dark 



edge entmema 



2c. Circumpeduncular scales 20; scales in transverse series to base of ventral 

 fin 5.5-1-4; gill rakers about 9+34; dorsal fin with a shai'ply defined 

 narrow dark border siamensis 



TYLOGNATHUS BRUNNEUS Fowler 



Tylognathus hrunneus Fowler, 1934a, p. 131, figs. 87, 88 (Chiengmai, Chiengsen) ; 

 1935a, p. 125 (Bangkok, Khao Nam I'oo). 



This species is unique among Thai members of the genus for its 

 absence of barbels. Numerous specimens from the Meping at Chieng- 

 mai, the Mekong at Chiengsen, and the basin of the Menam Chao Ph5^a 

 at Khao Nam Poo and Bangkok are from 4.1 to 19.1 cm. long. 



The original description gives 28 or 29 scales in the lateral line to the 

 base of the caudal fin and 3 more scales on the fin ; the figure, however, 

 shows only 27 scales in all. As the drawing on which the figure is 

 based was made by Mr. Fowler, the latter scale count has been used in 

 the key. 



TYLOGNATHUS CAUDIMACULATUS Fowler 



Tylognathus caudimaculatus Fowler, 1934a, p. 133, figs. 89, 90 (Chiengmai) ; 

 1935a, p. 125 (Srisawat). 



The type, 5.8 cm. long, and numerous other specimens, 3.2 to 5 cm. 

 long, came from the Meping at Chiengmai. A single specimen from 

 Srisawat was 12.7 cm. long. The species is comparatively plain, with 

 an obscure longitudinal dark stripe along middle of body becoming 

 more distinct posteriorly, and with a round black spot about size of 

 pupil on caudal peduncle, and the dorsal membranes are medianly dark 

 and have a gray free margin. 



A specimen, 9 cm. long, taken in the Menam Chao Phya at Bang 

 Pang, Central Thailand, November 25, 1923, is closer to T. caudimacu- 

 latus than any other species ascribed to that country but presents some 

 differences, which may be due in part to the larger size than specimens 

 described by Fowler, The specimen is a male, with the top of head, 



