These figures seem to be variants of that on folio 72 recto of the sketchbook (D10536; Turner Bequest CXL 65), and thus related to a seated figure lower left of centre in the Decline of the Carthaginian Empire (Tate N00499)1 exhibited at the Royal Academy in 1817. There are various drawings and drafts of verse connected with the picture in this sketchbook; see notes to folio 4 (D10416).
Martin Butlin and Evelyn Joll, The Paintings of J.M.W. Turner, revised ed. 1984, pp.100–1 no.135 (pl.137).