ἐξ ὀνύχων λέοντα τεκμαίρεσθαι → judge by the claws, judge by a slight but characteristic mark, small traits give the clue to the character of a person, deduce something from a small indication, identify a lion from its claws
P. and V. ἱμάς, ὁ, ῥυτήρ, ὁ, V. χαλινός, ὁ (Eur., Cyclops 461); see whip.