FRESH- WATER FISHES OF SlAM, OR THAILAND 281 



Genus HEMIMYZON Regan 



Hemimyzon Regan, Ann. Mag. Nat. Hist., ser. 8, vol. 8, p. 32, 1911. (Tj^pe, 

 Homaloptera formosana Boulenger.) 



HEMIMYZON FORMOSANUM (Boulenger) 



Homaloptera formosana Boulengeb, 1894b, p. 463 (Central Formosa). 



This species, described from Formosa, is entitled to a place in the 

 Thailand fauna from a specimen, 9 cm. long, in the British Museum 

 collected by Stockley in the Thaungyin Eiver, which forms a part 

 of the boundary between Thailand and Burma. 



Called Homaloptera by Boulenger, this fish was made the type of 

 the new genus Hemimyzon by Eegan in 1911. The outstanding generic 

 characters mentioned by Regan are the posteriorly converging bases 

 of the extended ventral fins and ventral rays numbering 15 or 16, with 

 the first 4 or 5 rays simple. Hora (1932, p. 298) amplified the very 

 brief generic diagnosis given by Regan and included in the genus 

 several Chinese species formerly placed in other genera. 



Family GYRINOCHEILIDAE 



In some respects the gyrinocheilids are the most remarkable of 

 Oriental fresh-water fishes, taxonomically and physiologically con- 

 sidered. Now placed in a distinct family, they have been variously 

 treated by authors since the first species was described. Vaillant, who 

 established the type genus Gyrinocheilus in 1902, placed it in the sub- 

 family Homalopterinae. Boulenger (1904, p. 582) thought Gyrin- 

 ocheilus should be regarded as the type of a distinct subfamily of 

 cyprinidae, coordinate with Catostominae, Cyprininae, Cobitidinae, 

 and Homalopterinae. Later Regan felt that the proper place for the 

 genus was in the Cyprinidae, close to Grossocheilus and Discognathus^ 

 and Weber and de Beaufort (1916, vol. 3) accepted that allocation 

 without comment. Berg (1906), in connection with the description 

 of a new species {Gyrinocheilus haznakovi) from Thailand, definitely 

 established the subfamily Gyrinocheilinae for its accommodation. Jor- 

 dan (1923) placed the genus without comment in both the Cyprinidae 

 and the Homalopteridae. It remained for Hora (1923b) to give these 

 fishes full family rank, and one need have no hesitation in following 

 him, for they exhibit a combination of peculiar features : Mouth struc- 

 ture, absence of pharyngeal teeth, presence of both exhalent and in- 

 halent gill openings, and other characters, which taxonomically are 

 quite as significant as those that are used to separate the Cobitidae and 

 Homalopteridae from the Cyprinidae. 



The family is herein recognized as having a single genus. Gyrin- 

 ocheilops^ as established by Fowler ( 1937) , is not acceptable as a genus 



