The headword is neuter nominative/accusative plural of mnhmh/i+on, Ionic for mnhmei=on. Same entry in Photius (mu485 Theodoridis) and other lexica, and similarly in various tragedic scholia. The singular occurs (e.g.) twice in Herodotus; the present plural is perhaps extracted from Apollonius Rhodius, Argonautica 4.28. [The TLG online text of Megasthenes FGrH 715 F15 claims another instance there, but it is problematic: neither Jacoby ad loc. nor P.A. Brunt in the Loeb edition of this non-verbatim fragment's source (Arrian, Indica 10), nor the text of Arrian on TLG (from the edition of Roos & Wirth), show it as anything other than the expected mnhmei=a.]
For the glossing word see also also epsilon 277.