eigenmann: the FRESHWATER FISHES OF BRITISH GUIANA 189 



One specimen, 84 mm. Georgetown. (C. M. Cat. No. 1641.) 



Twenty specimens, 53-112 mm. Gluck Island. (C. M. Cat. No. 1642a-c; 

 I. U. Cat. No. 12032.) 



Head 3.75-4; depth equals head; width 3.16; D. 1,5; A. 10 or 11; lateral 

 plates 2 or 3 + 22 to 27; eye 2.5 in snout, 9 in head, 3.5-4 in interorbital. 



Ventral surfaces of coracoid not exposed; head depressed, flat between the 

 eyes, becoming slightly arched in the nuchal region, not roof-shaped, granulated 

 to between the anterior nares; posterior nares just in front of the supraorbital 

 ridge, scarcely protected by the low nasal bone; orbital margin, preopercle and 

 opercle granular in the adult; maxillary barbel reaching to second third of humeral 

 process in the adult, beyond its tip in the young; outer mental barbels scarcely 

 shorter than the maxillary. Jaws equal or the upper but slightly longer; mouth 

 strictly terminal, its width less than half the distance between the gill-openings. 



Pectoral spine strongly serrate on anterior and posterior margins; upper sur- 

 face in young with a median series of straight teeth, in the adult with numerous 

 irregularly placed teeth; lower surface rough in young, striate in adult; dorsal spine 

 about two-thirds the length of the pectoral spine, its posterior surface smooth, its 

 anterior surface with a series of straight spines, its sides with one or more series 

 of similar spines; caudal rounded, humeral process reaching third fourth or fourth 

 fifth of pectoral spine, with a series of large recurved spines in young, and smaller 

 spines above them, the difference between large and small spines becoming less 

 with age; lateral plates highest above origin of anal, those of opposite sides meeting 

 along the median line from near the tip of the dorsal to the caudal and along the 

 ventral line of the caudal peduncle; median spine of plates nearly straight, each 

 plate from about the seventh with a series of teeth increasing in size toward the 

 upper and lower margins; anterior plates with more numerous smaller spines. 



Black; a light median line along back of head and sometimes body; a light 

 line from posterior nares following margin of skull and then along median line of 

 spines. Caudal black, with hyaline bars; other fins black with hyaline blotches or 

 bands; posterior margin of adipose light; lower surface and sides of head marbled. 



Oxydoras Kner. 

 Oxydoras Kner, SB. Akad. Wiss. Wien, XVII, 1855, 115 (sp.); Bleeker, Nederl. 



Tijdschr. Dierk., I, 1863, 14 (niger). 

 Pseudodoras Bleeker, Ichth. Arch. Ind. Prodr., I, 1858, 53 (niger). 

 Rhinodoras Bleeker, Nederl. Tijdschr. Dierk., I, 1863, 14 (Orbignyi). 



Type, Doras niger Valenciennes. 



Doradines with the barbels simple; no teeth; eye in posterior half of head, 

 snout long and pointed. 



