FRESH-WATER FISflES OF SIAM, OR THAILAND 257 



free edge of rostrum covering base of upper lip, continuous lips, 

 trenchant lower jaw, barbels, squamation, and fin rays, but differs in 

 having the edge of the rostrum crenulated and medianly incised, in 

 having no fleshy superficial padlike part of lower lip, in having a deep 

 postlabial groove that almost cuts off the outer segment of each side of 

 the lower lip, and in the division of the snout into central and lateral 

 parts by a deep groove, which extends upward and forward from the 

 side of the mouth. 



Resemblance to Ldbeo is in the general mouth structure, but differ- 

 ence is seen in the median division of the thin crenulated rostral flap, 

 in the bilobed shape of the flap, in the lower lip closely adnate to the 

 lower jaw, and in the absence of inner transverse labial folds. 



HENICORHYNCHUS LOBATUS, new species 

 FiGUBE 49 



Desoription. — ^Form elongate and moderately compressed; dorsal 

 and ventral profiles similar ; depth 3.5 in standard length ; least depth 

 of caudal peduncle 1.5 in its length and about 2 in head; head 4.3 in 

 length; eye 3.8 in head, 1.2 in snout, and 1.6 in the broadly convex 

 interorbital space, a narrow circular orbital rim best developed an- 

 teriorly ; snout broadly rounded, 3 in head ; nostrils large, in horizontal 

 line with upper edge of pupil ; mouth wide, horizontal, lips thin and 

 continuous ; upper lip medianly covered by a rostral flap, whose sur- 

 face is finely papillate, its edge crenulate and divided by a deep 

 emargination into two rounded lobes ; lower lip very thin and closely 

 adnate to jaw, its central part continuous with skin of isthmus, its 

 lateral parts with a postlabial groove, which almost completely sepa- 

 rates them from the center; lower jaw with a broad, thin trenchant 

 edge; a deep groove on each side of mouth extending from behind 

 labial commissure upward and forward to a point on snout opposite 

 pupil, forming a well-marked central lobe; a concealed barbel, 0.25 

 diameter of eye, behind the commissure; branchial aperture wide, 

 extending forward to a point under posterior border of eye ; branchial 

 membranes joined to the narrow isthmus; gill rakers short, slender, 

 about 5+29 on first arch; pharyngeal teeth 5, 4, 2, long, close-set, with 

 broad grinding surface. 



Squamation: Scales in lateral line 35, in transverse line 14 from 

 midline of back to midline of abdomen, 5 between lateral line and 

 base of ventral fin, 9 predorsal, 20 circumpeduncular; lateral line 

 gently decurved in first fourth of its length, thence running nearly 

 straight to midcaudal base. 



Fins: Dorsal rays ii, 8, first branched ray somewhat longer than 

 head, last simple ray slender and scarcely or not at all osseous, free 

 edge of fin concave ; origin of dorsal fin well in advance of ventrals, 

 over ninth scale of lateral line and much nearer to tip of snout than 



