Ageneiosus

1. Caudal fin truncate; body deep, its depth contained 4.5 to 5 times in standard length ................................. A. inermis

1’. Caudal fin bifurcate; body elongated, its depth contained 5.7 to 7.5 times in standard length...................... 2

2. Dorsum with a black longitudinal band, sometimes interrupted by light-beige irregular blotches; mouth cleft inverted U-shaped in ventral view ...................... A. militaris

2’. Dorsum uniformly dark-grey; mouth cleft inverted V-shaped in ventral view................................ A. ucayalensis