23 
2 a. Dorsal fin origin in front of vent by a distance at least 
(lb) equal to depth of body — Anguilla reinhardti Steindachner : 
Long-finned eel. 
b. Dorsal fin origin ranging from behind, to not more than 
half body depth in front of vent— Anguilla australis 
Richardson : Short-finned eel. 
3 a. Tail fin tapering about a tapering body- ~ 4 . 
(Ic) b. Tail im fan-shaped or cleft, body ending abruptly — 5. 
4 a. Colour almost invariably mottled; surface of head between 
(3a) eyes without markings; diameter of eye greater than one- 
sixth length of head — Tandanus tandanus Mitchell : Fresh- 
water catfish. 
b. Colour rarely mottled; surface of head between eyes with 
longitudinal markings; diameter of eye less than one- 
seventh length of head — Tandanus hyrtlii (Steindachner) ; 
Short-finned catfish. 
5 a. Single dorsal fin supported by fin rays, not divided into 
(3b) anterior spinous and posterior soft-rayed regions — 6. 
b. Dorsal fin divided into anterior spinous and posterior 
soft-rayed regions — 13. . 
c. Two dorsal fins separated by an appreciable finless 
region, the anterior spinous, the posterior entirely or 
almost entirely soft-rayed — 20. 
6 a. Small fatty fin-like body behind dorsal fin — 7 . 
(5a) b. No trace of fatty fin-like body behind dorsal fin — 8. 
7 a. Dorsal fin between levels of pectoral and ventral fins. 
(6a) Tail deeply cleft. (Pectoral with prominent spines) — 
Netuma thalassina (Ruppell) : Salmon catfish. 
b. Dorsal fin at about level of ventral fin; tail emarginate. 
(Fatty fin prominent) — Salmo gairdnerii Richardson ; 
Rainbow trout. 
c. Dorsal fin at about level of anal fin; tail cleft. (Fatty fin 
small) — Retropinna semoni (Weber) : Australian smelt. 
8 a. Origin of dorsal fin at level of ventral fin — 9. 
b. Origin of dorsal fin at level of or behind anal fin —12. 
9 a. Dorsal fin with leading edge a saw-edged spine and 
(8a) without a trailing filament — Carps, 10. 
b. Dorsal fin without leading spine and with a trailing fila- 
ment. (Tail deeply cleft) — 11. 
10 a. Dorsal fin with rounded margin. Scales on lateral line 
(9a) 
spinous dorsal fin 
ventral 
paired fir, 
