16 Annals of the Carnegie Museum. 



Scales regularly and deeply imbricate, each with several divergent 

 striae. Anal sheath of a few scales in a single row near front of 

 anal ; lateral line but little decurved ; caudal scaled for about one- 

 fourth of its length. 



Origin of dorsal in front of middle of body, but little more remote 

 from snout than dorsal ; highest dorsal ray about 2jA, in the length; 

 caudal deeply forked, the lobes longer than the dorsal ; anal deeply 

 emarginate ; ventrals not reaching anal, pectorals just to ventrals. 



No humeral spot ; caudal with a small diffuse dark spot at the base 

 of the middle rays. Scales of sides margined with dark, the marginal 

 spots tending to form dark lines along the sides ; pigment more profuse 

 toward the back ; a series of dark spots on the median series of scales 

 of the back. 



Named for Mr. S. E. Shideler, who as volunteer assistant collected 

 the species and gave most effective help during the entire expedition. 



Genus Astyanax Baird & Girard. 

 Astyanax guianensis sp. nov. 



Type, 54 mm. (No. 1013 Carnegie Museum Catalog of Fishes.) 

 Warraputa. 



Cotypes, 176 specimens, Rockstone, Essequibo River. (C. M. 

 Cat. No. 1014, a-z ; I. U. Cat. No. 117 17.) 



Cotypes, 2 specimens, 45-52 mm., Crab Falls, Essequibo River. 

 (C. M. Cat. No. 1015 ; I. U. Cat. No. 11718.) 



Cotypes, 2 specimens, 50-55 mm., Warraputa, Essequibo River. 

 (C. M. Cat. No. 1016; I. U. Cat. No. 11719.) 



Cotypes, 34 specimens, 43-55 mm -, Tumatumari, Potaro Kiver. 

 (C. M. Cat. No. 15 1 7, a-j \ I. U. Cat. No. 11720.) 



Allied to multidens, but without caudal spot. 



Head 4; depth 2.6-3 j D. 10 or 11 ; A. 25-27 ; scales 5-34 or 35 

 (rarely 36)-4 ; eye 2.33 ; interorbital 3. 



Compressed, subrhomboidal, ventral profile regularly arched ; 

 dorsal profile with an angle at the origin of the dorsal, slightly 

 depressed over the eye ; preventral area rounded, tending to flattish, 

 with a median series of scales sometimes irregular in the middle ; post- 

 ventral area narrowly rounded ; predorsal area rounded, with a median 

 series of nine scales. 



Occipital process about 4 times in the distance from its base to the 

 dorsal, bordered by three scales on the sides ; interorbital flat, with 



