FRESH-WATER FISHES OF SIAM, OR THAILAND 61 



Giinther (1861, vol. 3, p. 539) placed them between the trumpetfishes 

 (Fistulariidae) and the springbacks (Notacanthidae) and wrote: 

 "The structure of the mouth (not of the bones of the upper jaw) and 

 of the gill-apparatus, the separation of the humeral arch from the 

 skull, the absence of ventral fins, the anatomy of the internal parts, 

 and the whole habit, afforded ample proof that these fishes are eels, 

 in which a part of the dorsal fin is spinous." 



Boulenger (1904, p. 716) placed them in the suborder Opisthomi, 

 between the suborder Acanthopterygii and the suborder Pediculati, 

 and stated: "This division stands in the same relation to the Acan- 

 thopterygii as do the Apodes to the Malacopterygii. The single 

 family is possibly derived from the Blenniidae." 



Jordan (1923) placed them in the order Opisthomi immediately 

 preceding the Apodes. 



The family comprises two closely related genera, both represented 

 in Thailand, one by a single species, the other by eight species. 



la. Under surface of rostral appendage marked by transverse striae ; no spines 

 at angle of preopercle Macrognathus 



lb. Under surface of rostral appendage without transverse striae; spines at 

 angle of preopercle in most species Mastocembelus 



Genus MACROGNATHUS Laeepede 



Macrognathus Lacepede, Histoire uaturelle des poissous, vol. 2, p. 283, 1800. 

 (Type, Ophidium aculeatum Bloch, restricted by Cuvier and "Valenciennes, 

 1831.) 



MACROGNATHUS ACULEATUS (Bloch) 



Ophidium aculeatum Bloch, 1787, vol. 5, p. 60, pi. 159, fig. 2 (East Indies). 

 RhynchoMella aculeata var. siamensis Guntheb, 1861, vol. 3, p. 540 (Petchaburi). 

 RhynchoMella ocellata Bleeker, 1865 (347), p. 34 (Siam) ; 1865 (356), p. 174 



(Siam). 

 Rhynchohdella aculeata von Martens, 1876, p. 396 (Bangkok). — Sauvage, 1883b, 



p. 151 (Menam Chao Phya).— Hora, 1923b, p. 180 (Bangkok).— Chabanatjd, 



1924, p. 580 (Gulf of Siam).— Fowler, 1934a, p. 146 (Chantubun) ; 1935a, p. 



134 (Bangkok) ; 1935b, p. 513 (Old Chiengsen) ; 1937, p. 222 (Bangkok, 



Tachin, Mepoon, Kemarat). 

 Rhyncobdella aculeata Sauvage, 1881, p. 160 (Siam, Mekong). 



The range of this species extends from India to Burma, Thailand, 

 Indo-China, Malaya, and some of the East Indian islands (Borneo, 

 Moluccas) . According to Hora ( 1923b) , the fish "is found in brackish 

 waters within tidal influence and in the deltas of Indian, Burmese 

 and Sind rivers." In Thailand, however, the fish is race in brackish or 

 coastal waters and is mostly to be met with far from the sea, through- 

 out the Menam Chao PHya, in the Menam Sak as far upstream as 

 Pechabun, in the Menam Chi at Udon, as far inland as Kemarat, 

 and in tributaries of the Menam Mao, and in various lakes, swamps, 

 canals, and ditches of the central plain. 



