166 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



They exhibit a wide range in size, the smallest species being only 

 an inch in length, the largest more than a foot. Regardless of size, 

 they are eaten by the local people, and, on account of their general 

 abundance and ease of capture, constitute an important element in 

 the food supply. 



While most of the species are plain silvery without distinguishing 

 marks, some are brilliant golden, some are strikingly spotted or cross- 

 banded, and some have beautiful red, blue, and other colors on head, 

 body, and fins. In addition to the 31 species shown in the following 

 key, there have been ascribed to Thailand a few others of invalid or 

 doubtful status that are noted at the end of the regular series. Some 

 of the local species are unfortunately known from sparse material, in 

 some cases from single specimens, so that intraspecific variability 

 cannot be determined. 



la. No barbels. 

 2a. Last simple dorsal ray osseous and denticulated, much longer than head; 

 last simple anal ray osseous and strong; scales in lateral line 37; 

 scales in transverse series to base of ventral fin 7-1-4.5 ; body marked 



by oblique blackish bands; size medium bulu 



2b. Last simple dorsal ray nonosseous and nondenticulated, much shorter than 

 head ; last simple anal ray nonosseous and weak ; scales in lateral line 

 22 to 25 ; scales in transverse series to base of ventral fin 4 or 5-1-3 ; a 

 round or vertically elongate spot at third scale of latei'al line, another 

 such spot on caudal peduncle at posterior end of anal base ; size 



small stoliczkae 



1&. Two barbels (maxillary). 

 3a. Last simple dorsal ray nonosseous and smooth ; lateral line incomplete ; 

 only first G scales bearing tubules; scales around caudal peduncle 12; a 

 black spot on caudal peduncle, another black spot on basal part of 



dorsal fin masyai 



36. Last simple dorsal ray osseous and smooth ; lateral line complete ; scales 

 in lateral line 23 to 26. 

 4a. No black spot on dorsal fin ; a black spot on caudal peduncle ; scales 



around caudal peduncle 12, 14, or 16 leiacanthus 



4b. Usually a black spot on basal part of soft dorsal rays and a black spot 

 on caudal peduncle. 

 5a. A dark median band and a dark margin on dorsal fin ; a narrow dark 

 longitudinal stripe on body ; scales around caudal peduncle 12. 



spilopterus 

 5&. No dark median band and no dark margin on dorsal fin ; no dark 

 longitudinal stripe on body ; scales around caudal peduncle 16. 



sophoroides 

 3c. Last simple dorsal ray osseous and denticulated ; lateral line complete or 

 incomplete. 

 6a. Lateral line incomplete; body deep (depth 2.12 to 2.2) ; maxillary barbel 

 about 0.5 eye; head and body marked by 5 black cross bands. 



partipentazona 



66. Lateral line complete; depth 2.3; maxillary shorter than eye; no dark 



spots on dorsal fin; sides without bars or spots; base of dorsal and 



anal with a few scales ; dorsal fin origin over ninth scale of lateral line, 



midway between tip of snout and base of caudal fin viehoeveri 



