272 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



lip but sending a frenulum to lateral part of lower jaw; gill mem- 

 branes broadly joined to tlie isthmus; dorsal fin with 10 branched 

 rays. 



The pharyngeal teeth present interesting features. In the original 

 description of Mekongina erythrospila these teeth are given as in 

 two rows (3,5-5,3), but there is an entirely different formula in one 

 of the two specimens in hand whose teeth have been removed. On 

 each side the teeth are in three rows, with five in the main row, four 

 in the second row, and two in the third row. Outside the main row 

 and parallel and in close approximation therewith there is on each 

 side a row of full-sized teeth, four on the right side, three on the 

 left side, which are not inserted in the pharyngeal bone but are 

 loosely attached by fibrous tissue; and on the left side there is a 

 similar single tooth at one end of each of the second and third rows. 

 It may be inferred that these freely movable teeth with no bony 

 attachment have been displaced by new teeth and would ultimately 

 have become completely shed. A further peculiarity is that between 

 the ultimate and penultimate teeth at one end of the main row on 

 the right side a small tooth (not enumerated in the foregoing count) 

 is visible. 



The describer of the genus Mekongina compared it only with Ldbeo^ 

 from which it "differs in its lip structure and the absence of barbels." 

 Mekongina, however, belongs in a different group of the Cyprininae, 

 characterized by the entire absence of a special rostral fold and the 

 continuation of the rostral skin as the upper lip. The relations are 

 closest with Crossocheilus, in which, as in Mekongina, the lips are 

 not continuous, but in Grossocheilus there are barbels in one or two 

 pairs and the dorsal fin has only 8 branched rays, against 10 in 

 Mekongina. On the basis of these differences, the genus Mekongina 

 may be retained as distinct. 



MEKONGINA ERYTHROSPILA Fowler 



Mekongina erythrospila Fowled, 1937, p. 200, figs. 161, 162 (Kemarat). 



The fish representing this genus and species is known as yet only 

 from the Mekong at Kemarat in Eastern Thailand. Numerous speci- 

 mens, 7.3 to 19.3 cm. long, collected in 1936, are in the Academy of 

 Natural Sciences of Philadelphia and two in the U. S. National 

 Museum were received by exchange. 



Family HOMALOPTERIDAE 



Small loachlike fishes found in torrential streams of southern and 

 eastern Asia and the Indo-Australian Archipelago. Their shape and 

 structure, particularly that of the fins, adapt them to the peculiar ex- 

 actions of their environment. The best and most complete discussion 



