268 CALIFORNIA ACADEMY OF SCIENCES. 



Distance between the anterior and posterior nares about 

 one-fourth the diameter of the eye. 



Eyes large, the distance between their inferior margins 

 much less than between their superior margins, the di- 

 ameter of the eye 2-2f in head, 1 ; \ in interorbital. 



Mouth very small, inferior, its width less than a diam- 

 eter of the eye; lower jaw thin and pointed in front; all 

 the teeth villiform, the intermaxillary band with a back- 

 ward projecting angle on the outer margin. 



Distance of dorsal spine from the snout 2J 2| in the 

 length; dorsal spine roughened on both margins, higher 

 than the length of the head, 3f-3f in the length. Adi- 

 pose fin small, situated posterior to the anal fin. 



Caudal fin widely forked, the lobes pointed, 3J-4 in 

 the length. Anal fin very short. 



Pectoral spine slender, smooth on the sides, roughened 

 in front, short teeth along its entire margin behind, 

 about reaching the ventral fin, 2| in the length. 



Back chocolate with black dots, usually a plumbeous 

 lateral band, becoming abruptly silvery below; the sides 

 sometimes punctate with black or dark brown; top of 

 head and around the eyes dotted with black, opercles sil- 

 very, sometimes punctate; sometimes the humeral region 

 is yellow and the belly golden; caudal, ventral and pec- 

 toral fins more or less dusky. This species has the gen- 

 eral appearance of an Exocwtus. 



Head 3|-4, to end of dorsal plate 2|-2|; depth 6; 

 D. I, 5-6; A. 7; V. 6; P. I, 6-10. 



Over ninety specimens examined, the largest measur- 

 ing .08 m. Villa Bella; Obidos; Para; Tabatinga; Gu- 

 rupa; Manacapuru; Lago Alexo; Hyavary. 



207, Centromochlus steindachneri, 



Centromochlus steindachneri Gill, Proc. Acad. Nat. Sci. Philad. 1870, 



95 (Upper Amazon). 

 Habitat: Upper Amazon. 



