ἆρ᾽ οὖν δὴ διεληλύθαμεν ἤδη καθάπερ χθές, ὡς ἐν κεφαλαίοις πάλιν ἐπανελθεῖν, ἢ ποθοῦμεν ἔτι τι τῶν ῥηθέντων, ὦ φίλε Γίμαιε, ὡς ἀπολειπόμενον;
The ὡς ἐν κεφαλαίοις πάλιν ἐπανελθεῖν is I think an absolute inf, which should have been registered as such by dictionaries or grammars.