406 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



Phya December 22, 1923, had large transparent orange-red eggs nearly 

 or quite ready for extrusion. 



The various species of Osteogeneiosus described by Bleeker and 

 properly placed by Weber and de Beaufort in the synonymy of 0. 

 militaris were for the most part based on such characters as the rela- 

 tive proportions of length of body, depth of body, and length of head, 

 in apparent ignorance of the variations due to sex. 



In Thailand this fish has little repute as food, and is one of the 

 cheapest in the markets. In India a poor quality of isinglass is made 

 from its swim bladder. 



This fish is known by a variety of names in different parts of its 

 Thailand range. Often it is not distinguished from species of Tachy- 

 surus and is given the same names, pla hot and fla uk (in allusion to 

 the sound made by the fish), with or without qualifying words, such 

 as pla hot hua on {hua on, soft head), pla hot nud, pla hot hokaso, 

 pla hot sorn oui {som oui, buxom or plump) , and others. In Peninsular 

 Siam, as in the Tale Sap, the name pla hot hua on may be shortened 

 to pla hua on. In the Bangpakong River a name in use is pla uh hua 

 son. 



Genus TACHYSURUS Lacepede 



Tachysurus Lacepede, Histoire naturelle des poissons, vol. 5, p. 150, 1803. (Type, 

 Tachj/survs sinensis Lacepede.) 



Some of the fishes of this genus are found regularly in fresh water 

 in Thailand, but the genus is primarily marine. It seems desirable, 

 however, to include in this account all the species known from Thailand 

 rather than to attempt an artificial separation. 



The number of species is large, and some of them are very abundant 

 and economically important. 



Oral incubation has been observed in nearly all the local species, and 

 it seems probable that this habit is common to the genus. 



Secondary sexual characters are marked, involving the shape and 

 size of the head, the position and shape of some of the fins, and the 

 development of special appendages on the ventral fins. 



There has been no opportunity to observe the spawning habits, and 

 it is not known how fertilization of the eggs is effected and how the 

 eggs are taken into the mouth of the male. During the protracted 

 period of hatching, which may cover 6 to 8 weeks, the male takes no 

 food, and his fasting is further prolonged by the retention of the young 

 in his mouth until the complete or partial absorption of the yolk sac. 

 By the time the young have left the shelter of the parental mouth, the 

 male undergoes considerable emaciation, and it may be assumed that 

 in fishes as ravenous and gluttonous as the catfishes the spawning season 

 is a time of great stress for the males. 



