126 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



inferior in Anihlyrhynchichthys^ high on snout and superior in 

 Sikukia). 



SIKUKIA STEJNEGERI H. M. Smith 



Sikukia steinegcri Smith, 1931e, p. 138 (Sikuk River). 



The type specimen of this species, 11 cm. long, taken in the Sikuk 

 River, Central Thailand, November 26, 1923, remains unique, except 

 for a specimen, 6.9 cm. long, from tlie Pasak River, Central Thailand, 

 August 20, 1923. 



Genus MYSTACOLEUCUS Gunther 



Mystacoleucus Gunther, Catalogue of the fishes in the British Museum, vol. 7, 

 p. 206, 1868. (Type, Sysiomus (Capocta) padangensis Bleeker.) 



Although Giinther established this very distinct genus, he failed to 

 mention or recognize its most outstanding character, namely, the 

 presence of a procumbent predorsal spine ; and he listed in the com- 

 plex genus Barbus^ under the name Barbus obtusirostris^ a species 

 [marginatus) that properly belongs in Mystacoleucus. 



The essential features and limitations of this genus are : Body mod- 

 erately elongate, more or less strongly compressed; abdomen rounded; 

 head small; eye comparatively large, pupil or entire eye in advance 

 of midlength of head ; snout poriferous, overhanging small, strongly 

 arched subterminal or slightly inferior mouth; lips thin, continuous 

 around corners of mouth, upper lip separated from skin of snout by 

 a deej) groove, lower lip closely adnate to jaw, a postlabial groove 

 on each side; barbels four (rostral and maxillary), two (maxillary), 

 or none ; pharyngeal teeth 4, 3, 2, uncinate ; gill membranes narrowly 

 joined to isthmus at or slightly behind vertical from posterior border 

 of eye ; gill rakers few, short, wide-spaced, spinous or conical ; scales 

 of moderate size, extending on nape approximately over anterior 

 border of opercle; lateral line complete, extending along middle of 

 caudal peduncle; a procumbent predorsal spine which may perforate 

 first, second, or third f>redorsal scale, or may be concealed by scales; 

 dorsal fin arising about opposite base of ventrals, its last simple ray 

 osseous and denticulated or non-osseous and simple, branched rays 

 eight or nine ; branched anal rays six to ten. 



Because of important nomenclatural and taxonomic questions in- 

 volved, it seems desirable to refer in this place to a paper l3y Dr. Hora 

 (1937f ) in which, in a discussion of cyprinoid fishes with a procumbent 

 predorsal spine, he placed the well-lmov/n Indian fish Rohtee og'tlhii 

 Sykes (1839) in the genus Mystacoleucus for the reason that he found 

 in a number of specimens in the Indian Museum a procumbent pre- 

 dorsal spine, which in some of them was obvious, in others was con- 

 cealed by scales. Of the half dozen species of Rohtee, only og'dbii 

 was involved in this reallocation. In a subsequent paper Hora ( 1939, 



