Moenkhausia

1. Dark-brown blotch on posterior portion of caudal peduncle and proximal third of caudal-fin base, occupying their whole depth; caudal-fin lobes hyaline ........................ 2

1’. Dark-brown blotch on caudal peduncle and caudalfin base absent or, if present, restricted to the midlateral portion of the caudal peduncle (not covering its whole depth) .................................................................................. 4

2. Lateral line disrupted or completely pored ..... M. australe

2’. Lateral line incompletely pored..................................... 3

3. Transversal series above lateral line with 4 scale rows, and below lateral line with 3 scale rows ............................ .............................................................. M. sanctaefilomenae

3’. Transversal series above lateral line with 5 scale rows, and below lateral line with 4 scale rows ............... M. forestii 4. Distal portion of upper caudal-fin lobe darker than the lower ........................................................... M. cf. gracilima

4’. Distal portion of caudal-fin lobes equally pigmented. 5

5. Distal portion and distal margin of caudal-fin lobes dark-brown; silvery longitudinal stripe (brown or grey on preserved specimens), from vertical through dorsalfin origin to median caudal-fin rays, widened on the posterior portion of caudal peduncle to form a blotch; first gill arch with seven gill rakers on upper limb and 12 on lower limb ...................................................... M. bonita

5’. Distal portion of caudal-fin lobes dark-brown and distal margin hyaline; silvery longitudinal stripe (brown or grey on fixed specimens), from opercle to caudal peduncle, not forming a blotch on the posterior portion of caudal peduncle; first gill arch with 10 gill rakers on the upper limb and 18 on lower limb ....................... M. aff. intermedia