312 MEMOIRS OF THE CARNEGIE MUSEUM 



166. Odontostilbe melandetus sp. nov. (Plate XLIV, fig. 3.) 



Type, 27 mm. Locality? (Carnegie Museum Catalog of Fishes No. 1878.) 



Cotypes, three specimens, about 27-35 mm. Locality? (I. U. Cat. No. 

 12160.) 



Readily distinguished by the black margin of the caudal peduncle. 



Head 3.75; depth 3.6; D. 10; A. 21; scales 4-34 or 35-3. Eye 2.5-2.7 in the 

 head; interorbital but little narrower than the eye. 



Minute, compressed, head bluntish, the mouth terminal; a median series of 

 ten scales in front of the dorsal. Maxillary very slender, reaching to below the eye; 

 maxillary-premaxillary border as long as the eye; ten to fourteen teeth on the pre- 

 maxillary, four to seven on the maxillary. 



Scales very regularly imbricate, with concentric, but without longitudinal, 

 stria?; lateral line complete, scarcely decurved; anal naked; base of caudal with 

 a few scales. 



Fins all well-developed, the anal deeply emarginate; pectorals not quite reach- 

 ing ventrals, ventrals not to anal. 



No chromatophores on the sides; scales of the back with marginal series of 

 chromatophores; a series of black specks along the base of the anal, the caudal 

 peduncle margined with black. 



Aphyocharax 35 Gunther. 

 Aphyocharax Gunther, Proc. Zool. Soc. London, 1868, 254. 



Type, Aphyocharax pusillus Gunther. 



Minute, slender fishes, with a single series of tricuspid teeth in the premaxillary, 

 and a few teeth in the maxillary. Lateral line incomplete; gill-membranes free 

 from the isthmus; a frontal and a parietal fontanel. 



Key to the Guiana Species of Aphyocharax. 

 a. Dorsal with a black spot, humeral spot very faint, no caudal spot. A. 25; scales 5-7+25-2.. . melanotus. 

 aa. Dorsal without a black spot; anal plain; about fourteen scales in front of the dorsal; lateral line 34-37; 

 A. 17 erythrurus. 



167. Aphyocharax melanotus sp. nov. 



Type unique, about 43 mm. Rockstone sand-bank. (Carnegie Museum 

 Catalog of Fishes No. 1877.) 



This is the only Guiana species of the genus with a black dorsal spot. 



Head 4; depth 3.8; D. 10; A. 25; scales 5-6 + 27-2; eye much longer than 

 snout, 2.75 in head; interorbital 3.75 in the head. 



35 afyi-n, a small fish; charax, a genus of characins. 



