Sir Edmund Gosse
In the first dedicated discussion of Ephelia by a literary critic, Gosse suggested that if "Ephelia" had been "Joan Phillips," she might have been the daughter of the celebrated poet, Katherine ("Orinda") Philips (Seventeenth-Century Studies, 2d ed., 1885). Gosse's "wild rumor" (as he called his own hunch) was, indeed, "wild," and soon overturned by John Pavin Phillips of Haverfordwest, Wales, a descendant of the poet. On the basis of inscriptions in a family Bible, this relative showed that none of "Orinda"'s daughters were named Joan and none (alas) were writers (N&Q 1958, vol. V: 202ff).
Yet, some rumors die hard; for we find "Joan Phillips" (as Ephelia) inscribed in several extant copies of the rare Female Poems...by Ephelia. "Joan Phillips" is also listed as "Ephelia" in the principal American and British library catalogues, as well as in Donald Wing's Short-Title Catalogue. According to my present reading of the case, "Joan Phillips" was Mary Villiers's urban cover; and the longstanding attribution of Ephelia's work to Joan Phillips is not entirely wrong: it simply names one alter-ego (Ephelia) with another (Joan Phillips). Behind them both, was the chuckling Mary Villiers.
It may be some time before my new case is fully digested and hopefully accepted, at which point Wheatley's "Joan Phillips" would be superseded by Mary Villiers, the newly reclaimed Stuart duchess introduced in Section II of this essay. And this is all now underway: the "Ephelia" records in the ESTC/UK and ESTC/NA were updated to reflect Mary Villiers, in July, 2001.