To cite an excerpt from an anthology, follow the MLA format template. You will likely list a description in place of a title:

De Quincey, Thomas. Excerpt from Confessions of an English Opium-Eater. English Romantic Writers, edited by David Perkins, Harcourt, Brace, Jovanovich, 1967, pp. 725–30.

If the anthology provides original publication information for the work that is excerpted, you may list it in the optional-element slot at the end of the template:

Duyckinck, Evert A. “An Intellectual Chowder.” Moby-Dick, by Herman Melville, edited by Harrison Hayford and Hershel Parker, Norton Critical Edition, W. W. Norton, 1967, pp. 613–16. Excerpt from “Melville’s Moby-Dick; or, The Whale,” Literary World, vol. 9, 22 Nov. 1851, pp. 403–04.