FRESH-WATER FISHES OF SlAM, OR THAILAND 273 



of the classification, habits, and evolution of these fishes has been 

 givenbyHora (1932). 



The family falls in two subfamilies. In addition to osteological 

 characters, as indicated by Hora (1932) , the most obvious difference is 

 in the degree of simplification of the rays of the paired fins. In the 

 Homalopterinae, at least 2, and in some genera 3, 4, or 5, of the anterior 

 ventral rays are simple; and in the various genera from 4 to 13 of 

 the anterior pectoral rays are simple. In the Gastromyzoninae only 

 one ray in the ventral and pectoral fins is simple. 



Of the genera recognized as inhabiting Thailand, one is of wide dis- 

 tribution (Northern, Central, Peninsular, and Southeastern Thai- 

 land), two are as yet known only from the Thailand-Burmese bound- 

 ary, and one is herein described as new from Peninsular Thailand. 

 They have the following characterization : 



la. Two or more of the anterior rays of the ventral and pectoral fins undivided. 

 Subfamily Homalopterinae. 

 2a. No deep preoral groove extending around corners of mouth ; lips not pap- 

 illate ; a single barbel at each corner of mouth, in addition to 2 pairs of 

 rostral barbels; ventral rays 8 to 10, the 2 outer rays unbranched; 



pectoral rays 14 to 30, the 4 to 8 outer rays unbranched Homaloptera 



2b. A deep preoral groove extending around corners of mouth ; lips papillate. 

 3a. Ventral rays 10 or 11, the 2 outer rays unbranched ; a single barbel at 

 each corner of mouth, in addition to 2 pairs of rostral barbels. 

 4a. Body and head greatly depressed; ventral fins not reaching ventral 

 opening, which is nearer to anal fin than to base of ventrals; pec- 

 toral fin beginning under eye, the rays 19 to 21, with 8 to 10 outer 



rays unbranched Balitora 



4b. Body cylindrical, head greatly depressed ; ventral fins extending be- 

 yond ventral opening, which is much nearer to base of ventrals than 

 to anal fin ; pectoral fin beginning posterior to eye, the rays 14, with 



4 outer rays unbranched Balitoropsis 



3&. Ventral rays 12 to IS, the 4 or 5 outer rays unbranched ; pectoral rays 

 22 to 26, with 11 to 13 outer rays unbranched ; 2 barbels at each corner 



of mouth in addition to 2 pairs of rostral barbels Hemimyzon 



1&. Only the first ray of the ventral and pectoral fins undivided. Subfamily 

 Gastromyzoninae (no local species yet known). 



Subfamily Homalopterinae 



Genus HOMALOPTERA van Hasselt 



Homaloptera van Hasselt, Alg. Konst. Letterbode, vol. 2, p. 133, 1823. (Type, 

 Homaloptera fasciata van Hasselt.) 



This is the most numerous genus of homalopterid fishes, and in 

 Thailand is represented by six species, none exceeding 10 cm. in length 

 and most of them much smaller. The genus is otherwise known from 

 the Indo-Australian Archipelago and the southern and southeastern 

 Asiatic mainland, being especially well represented in Java, Sumatra, 

 and Borneo. 



