A few scholars have long puzzled over the fact that some of the unauthorized editions of Shelley's poems which were published after Posthumous Poems (London, 1824, edited by Mrs. Shelley) contain better readings at certain points than that volume, readings which do not appear in an authorized text until Mrs. Shelley published The Poetical Works of Percy Bysshe Shelley in 1839 (London, four vols.). Robert Browning noticed this in a letter addressed to H. Buxton Forman, dated 2 July 1877, in which he says of the fifth line of “Stanzas Written in Dejection, near Naples,” omitted in the body of the text of 1824, “The line was first restored in a strange edition of Shelley published by Benbow in 1826; and Leigh Hunt, in 1828, quotes the poem without it, remarking on its loss: and it was myself who told him of its existence, to his surprise and pleasure.” Frederick A. Pottle, who quotes from Browning's letter in his Shelley and Browning (Chicago, 1923, p. 14), wonders how it was that Benbow obtained the missing line (p. 83). My investigation of this problem, instigated by Pottle, has led to two surprising discoveries: first, that all the modern editors of Shelley's text have failed to notice an errata leaf to Posthumous Poems which is present in some copies still extant, and, secondly, that there are important relationships between certain of the unauthorized editions which followed Posthumous Poems and Mrs. Shelley's text of 1839. These relationships, in fact, call into question the textual value of a large number of readings hitherto believed to be original to the first edition of 1839.