συννόμω, ‘having the same pasture’—here, ‘seeking their prey on the same ground.’ Cp. Hist. An. 6. 18 “οἱ ταῦροι ... ὄντες σύννομοι”. This primary sense of the adj. is here blended with the derived sense, ‘partners.’ The image is Homeric: cp. Il. 10. 297“βάν ῤ̔ ἴμεν ὥς τε λέοντε δύω διὰ νύκτα μέλαιναν” (Odysseus and Diomedes): cp. Il. 5. 548.So Aesch. Cho. 938“διπλοῦς λέων” (Orestes and Pylades): imitated by Eur. Or. 1401“λέοντες Ἕλλανες δύο διδύμω.” φυλάσσετον. Since neither can prevail without the other, each has the other's welfare in his keeping. We can perceive that the poet's mind glances from the metaphor to the thought of a “δίκαιος κἀγαθὸς παραστάτης” ( Ant. 671 n.).

