148 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



The characters on which Sauvage separated this species from G. 

 armatus^ namely, "les ecailles un peu plus petites, le profil rostro- 

 dorsal mois incline," in reality do not exist. Sauvage gave 38 scales 

 in the lateral line of his one example of C. dumerilii as against 33 to 

 36 in annatios, a difference of little significance, which disappears en- 

 tirely when put against the presence of 30 to 36 scales in the lateral 

 line of Thailand examples of C. dumerilii (Fowler). The steepness 

 of the rostrodorsal profile, which would determine the depth of the 

 body, varies with age ; although in specimens of O. armatus of the ap- 

 proximate size of the type of C. dimierilii the body is somewhat 

 deeper. 



If O. duTnerilii is separable from C. armatus^ its distinctive features 

 would seem to be the constant possession of two pairs of well-devel- 

 oped barbels (as against a single pair of maxillary barbels normally 

 in C. ai^iatus^ with a rudimentary pair of rostral barbels occasionally 

 present), and the slenderer caudal peduncle, its least depth contained 

 2.35 to 2.75 times in head (as against 1.75 to 1.85 times in C. armatus). 

 Furthermore, while C. dimierilii has no large round spot on the caudal 

 peduncle and no longitudinal rows of dark spots (one on each scale of 

 back and sides), these markings are always present in 0. armatus. 



The usual indigenous name for this fish is pla nam lang {nam lang, 

 back spine), but in places one hears the name pla takok^ both applied 

 also to other species of Cyclocheilichthys. 



CYCLOCHEILICHTHYS MEKONGENSIS Fowler 



Cyclocheilichthys meJcongensis Fowler, 1937, p. 187, figs. 126, 127 (Kemarat, 

 Pitsanulok). 



This species is based on numerous specimens from the Mekong at 

 Kemarat. Additional material was from the Nan River at Pitsanulok. 

 There are 4 short barbels, 34 or 35 scales in the lateral line, close-set 

 transverse sensory folds covering the entire surface of the head, an 

 oblique dark bar along the upper part of the gill opening, no con- 

 spicuous longitudinal dark lines on the back and side, and no dark 

 blotch on the caudal peduncle. 



A length of 15 cm. is attained. 



CYCLOCHEIUCHTHYS AMBLYCEPS Fowler 



Cychlocheilichthys aniblyceps Fowler, 1937, p. 187, figs. 140, 141 (Bangkok). 



Known from two specimens, apparently young, 10.4 and 9 cm. long, 

 from Bangkok. The snout is relatively short and the eye is relatively 

 large, as is characteristic of young cyprinoid fishes. With only two 

 specimens. Fowler makes an enigmatic remark about the barbels: 

 "Barbels minute to vestigial or even absent, rostral always smaller or 

 shorter, maxillary barely ^4 of eye." 



The species is very close to C. armatus. 



