FRESH- WATER FISHES OF SI AM, OR THAILAND 527 



described by Hamilton (1822) as Gobius sadanundio from the estu- 

 aries of the Ganges near Calcutta, as seems highly probably, this species 

 has a range extending from India and Burma to the Indo- Australian 

 Archipelago and Southeastern Thailand. Locally this fish thrives in 

 both brackish and fresh water, and, in addition to the estuary of the 

 Chantabun River, from which the type of Vaimosa spilopleura came, 

 it has been found to be common in the Menam Chao Phya at Bang- 

 kok, in the Bangpakong, and in the Tachin. 



A length of about 7 cm. is attained in Thailand. Bleeker re- 

 ported fish up to 8.5 cm. from Singapore and Java. 



Examples from a canal in Bangkok, kept in a small jar of fresh 

 water for several months, thrived on a diet consisting chiefly of 

 mosquito larvae, and increased in size. 



The fish shares with other gobies the vernacular name of pla hu. 



Genus ACENTROGOBIUS Bleeker 



AcentrogoUus Blkeker (453), Arch. N^erl. Sci. Nat., vol. 9, p. 321, 1874. (Type, 

 Gobius chlorostigma Bleeker.) 



Local species referable to this genus are numerous and not always 

 readily distinguishable from one another. They are mostly to be 

 found in estuaries and the mouths of rivers, and show a tendency 

 to extend their movements upstream, so that they are sometimes 

 captured in fresh water. 



The combination of features by which fishes of this genus may be 

 distinguished from Gtenogohius and Vaimosa, as indicated in the 

 key to the family, is: Squamation extending on the top of the head 

 to the posterior edge of the eyes; opercle and preopercle scaled, 

 partly scaled, or naked; teeth in several rows in each jaw, some of 

 them enlarged, with the outer row in the lower jaw extending only 

 half the length of the jaw and the last teeth recurved canines. In 

 Gtenogohius the head is entirely naked except, sometimes, for a line 

 or band of scales extending backward from each eye, and the teeth 

 are similar to those in Ace^itrogohius. In Vaimosa the top of the 

 head is scaled to the eyes and a patch of large scales more or 

 less covers the opercle ; and none of the teeth is enlarged. 



Very close to Acenfrogohius, and not always easily separable there- 

 from, are fishes assigned to the genus Gnatholepis. While Acentro- 

 gobius may have the preopercles and opercles fully scaled, in Gnatho- 

 le-pis these parts are always scaled, with the scales extending under the 

 eyes, usually in regular horizontal rows, and sometimes divided into 

 two or three groups or series by horizontal grooves. According to 

 Dr. Kouman's latest conclusions regarding these fishes, the only char- 

 acter separating Acentro gobius from Gnatholepis is the width of the 

 istlimus, which is wider in Acentrogobius because the gill openings 

 are more restricted. 



