254 PROCEEDINGS OF THE ACADEMY OF 



viii-12. Caudal fin subtruncate. The middle dorsal spines appear 

 to be longer than the posterior, but the latter with the two ante- 

 rior pointed raj-'s have been bitten nearly off, causing a deep and 

 regular emargination of the two fills, so that the normal form is 

 not certain. Pectoral and ventral fins extending to near the eighth 

 anal sjiine. Teeth in several series in both jaws, those of tlie ex- 

 ternal cylindric considerably larger. End of maxillary extending 

 but little behind tlie line of the posterior nareal opening. Profile 

 steep, concave and flat between the orbits, where its width a little 

 exceeds the diameter of the orbit. Latter one-third of head 

 equal length of muzzle. Depth of body 1.5 times the length 

 without caudal fin. 



Color dusky, with seven vertical blackish bars extending below 

 the basis of the dorsal fin, which break into spots on the bell}'; a 

 cross-bar through e^^e, and one across base of tail. Soft dorsal 

 with whitish cross-bars, other fins blackish. 



Total length .074 m.; to line of D. I. .02 m.; to line of A. I. 

 .03; to basis of caudal .055. 



This species is intermediate in characters in some respects be- 

 tween the species referred by Gunther to Uarus, Heckel (" Uaru^^), 

 and those referred to Ifesonauta, Giinther. I fail to perceive any 

 characters on which to establish the latter, and accordingly regard 

 its species as referable to the present genus. 



HEEOS BIMACULATUS, Linn. 



Acara bimnculata, Giiuther, 1. c. 276; A. gronotii, 'punctata et margarita, 

 Heckel fide Giiuther. 



This appears to be the only species of the Acaras of Giinther 

 which possesses four anal spines, the remaining species possessing 

 three. Heros, Heckel, is distinguished, according to the same, by 

 the possession of five spines in the anal fin. Out of eighteen speci- 

 mens of the present fish from the Amby iacu, four possess five spines? 

 the remainder four ; I am therefore disposed to define Acara as 

 having three, and Heros as having four or five anal spines, though 

 it is possible that it will be found necessary to unite the two 

 genera, 



[January 16, 



