512 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



Remarks. — ^This fish may be distinguished from the previously de- 

 scribed species of Ptereleotris by the reduced number of rays (19 or 

 20) in the anal and second dorsal fins (which rays in species of the 

 Indo-Australian Archipelago number 28 to 32 and in a Philippine 

 species 25), by the conspicuous jet-black spot on the base of the caudal 

 fin, and other characters. In P. heteropterus Bleeker from fresh 

 water in Borneo, the median caudal rays are black throughout and 

 the anal and second dorsal rays number 30 to 32. 



Family GOBIIDAE: Gobies 



As far as genera, species, and individuals are concerned, the great 

 majority of gobies belong to this family. Most of the local species 

 are small, and some of them exhibit much beauty of color, much 

 shapeliness of body, and interesting habits and habitats. Some spe- 

 cies are found as far inland as the headwaters of rivers in mountain 

 streams, in which the ventral cup assists in maintaining their posi- 

 tion; others inhabit the lower courses of the large rivers; a few live 

 indifferently in either fresh or brackish water; and many are estu- 

 arine or coastal. The genera herein recognized number 25. Those 

 most closely related are not always easily distinguishable from each 

 other, hence the following key must be used with discrimination : 



la. General shape elliptical ; body strongly compressed, the depth 2 to 3 times the 

 width ; dorsal tins contiguous or united basally ; ventral fins short, united, 

 forming a disk or tube ; gill openings restricted to sides, opposite base of 

 pectorals; teeth in several rows in each jaw, a pair of postsymphyseal 

 canines in lower jaw. 



2a. Head and body scaleless, covered with thick skin Gobiodon 



26. Head naked, body covered with large ctenoid scales Paragobiodon 



16. General shape moderately to very elongate; head and body compressed or 

 depressed ; head partly scaled to entirely naked ; body scaled or naked ; 

 dorsal fins well separated ; ventral fins wholly united and provided with a 

 basal membrane, or united only at their base and the basal membrane more 

 or less deficient ; gill openings restricted to sides or extending more or 

 less forward ; teeth in one, several, or numerous rows in each jaw. 

 3ff. First dorsal fin with 5 spines. 



4a. Teeth in both jaws uniserial ; head and anterior part of body scaleless, 

 body covered with weak ctenoid scales behind first dorsal fin ; second 

 dorsal fin with 8 branched rays, anal fin with 11 branched rays. 



Gobiopterus 

 46. Teeth in both jaws pluriserial ; head scaleless, body fully scaled ; second 

 dorsal and anal fins with 6 to 8 branched rays. 

 5a. Very elongate; mouth small, maxillary not reaching vertical from 

 anterior edge of eye; lower jaw with numerous short fleshy fila- 

 ments ; scales cycloid, about 39 in longitudal series Pipidonia 



56. Moderately elongate, mouth exceedingly large, maxillary extending on 

 preopercle; lower jaw with no fleshy filaments; scales ctenoid, 

 about 29 in longitudal series Eugnathogobius 



