Monographs

A plural subject may take a dual verb when the subject is a pair or two pairs: αἱ ἵπποι δραμέτην the span of mares ran Ψ 392.

a. This is common when δύο, ἄμφω, ἀμφότεροι are used with a plural subject: δύο ἄνδρες προσελθόντε Ἄ_γιδι διελεγέσθην μὴ ποιεῖν μάχην two men coming to Agis urged him not to fight T. 5.59. But even with these words the plural is preferred. The neuter plural with δύο rarely takes the dual verb (P. Tim. 56e).