Is that a spondee in your pocket or just a halting meter?

Today I received a spam email for online drugs. Nothing unusual in that. What was unusual, however, was the paragraph at the bottom of the message:

DAssouci, and at that time so popular in France, had no sanction from the ancient classic writers. Francisci Vavassoris opera omnia. Amsterdam. 1709. 16 The claims of Babrias also found a warm advocate in the learned Frenchman, M. Bayle, who, in his admirable dictionary, (Dictionnaire Historique et Critique de Pierre Bayle. Paris, 1820,) gives additional arguments in confirmation of the opinions of his learned predecessors, Nevelet and Vavassor. 17 Scazonic, or halting, iambics; a choliambic (a lame, halting iambic) differs from the iambic Senarius in always having a spondee or trichee for its last foot; the fifth foot, to avoid shortness of meter, being generally an iambic. See Fables of Babrias, translated by Rev. James Davies. Lockwood, 1860.

I would never even have thought to ask.