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.