312 MEMOIRS OF THE CARNEGIE MUSEUM 



106. 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 maxillar3\ 



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

 striae; 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^' Gimther. 



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



Type, Aphyocharax pusillus Giinther. 



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 erythruras. 



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 -f 27-2; eye much longer than 

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



^' d0iJ7), a small fish; charax, a genus of characins. 



