Apollo Shooting Arrows at the Children of Niobe
XVIII century. Wash, Pencil, Grey ink on blue paper. Not on displayAs J.A. Gere pointed out in 1981 (pencil note on the modern museum mount), the composition is taken from Polidoro´s facade decoration of the Palazzo Milesi, Rome. Judging from the style, the copyist was eighteenth century, which might imply he used an engraving or another drawing after Polidoro as his model, rather than the painted facade itself.
Turner, Nicholas, From Michelangelo to Annibale Carracc: a century of Italian drawings from the Prado, Virginia, Art Services International, 2008, p.361