502 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



2&. Eyes on short stalks and erectile above surface of head ; lower eyelid free 

 and movable; teeth in upper jaw in one or two rows; teeth in lower jaw 

 in one row, with no postsymphyseal canines ; pectoral fins with a 

 strongly developed muscular base; second dorsal fin with 12 to 15 

 branched rays Periophthalmidae 



2c. Eyes on short stalks or not; lower eyelid free and movable or not; teeth 

 in upper jaw in one row ; teeth in lower jaw in one horizontal row, with 

 or without a pair of postsymphyseal canines ; pectoral fins without a 

 strongly developed muscular base ; second dorsal fin with 13 to 31 



branched rays Apocrypteidae 



1 h. Form very elongate and more or less eellike ; a single very long dorsal fin, 

 anal fin very long, both joined to caudal or closely approximated 

 thereto Gobioididae 



6a. Ventral fins completely united into a funnel-shaped disk or more or less 

 separated and joined only at their base; above each opercle a slit 

 opening into a blind pouchlike cavity Trsrpaucheninae 



Oft. Ventral fins united ; no pouchlike cavity above opercle Gobioidinae 



Family ELEOTRIDAE: Sleepers 



The eleotrid gobies are characterized, among other features, by the 

 more or less complete separation of the ventral fins, which never form 

 a disklike sucking organ. They abound in bays and the mouths of 

 rivers, but some live exclusively on marine reefs, and some push their 

 way into the fresh parts of rivers or even into fresh-water lakes. 

 Those that have at times a fresh-water habitat are believed generally 

 to go into salt water to spawn. By far the largest of the gobies belong 

 in this family. 



These fishes lie quietly on the bottom, and are able to obtain pro- 

 tection by adapting their color or color pattern to the surrounding 

 bottom. 



Many of the local individuals of salt-water genera have a tendency 

 to push their way into the brackish or fresh parts of coastal streams; 

 and in order to render the treatment of the whole family more com- 

 plete all the genera represented in Thailand are included. They may 

 be differentiated as follows: 



la. Ventral fins with 4 branched rays; body very elongated and strongly com- 

 pressed ; scales very minute, embedded, cycloid, covering body posteriorly ; 

 no scales anterior to first dorsal fin; mouth very oblique; teeth small, 

 pluriserial, none canine or caninoid ; dorsal rays VI, 16 ; anal rays 15 ; 



caudal fin with several rays produced into filaments Herreolus 



1?>. Ventral fins with 5 branched rays. 



2a. Preopercle armed with a single decurved spine, which may be con- 

 cealed . Eleotris 



26. Preopercle unarmed. 



3a. Vomer with a -semioval patch of minute teeth ; a large black white-edged 

 ocellus at upper base of caudal fin; scales very small (130 to 140 in 

 longitudinal series) Bostrichthys 



