Unidentified Xema atricilla ? or Larus atricilla ?
Drawing depicting: Unidentified Xema atricilla ? or Larus atricilla ?, Finished tracing on tissue, graphited on reverse, developed from Gould 2042. Following the Gould conventions, the presence of a colored head and five spots on the primaries is clear (black and white respectively in the Black-winged Gull. The plate of Xema atricilla in Birds of Europe V: 426 is not related to these 2 drawings.