Razorbill <i>Alca torda</i> (left) and Little Auk <i>Alle alle</i> (right). This image comes from the book Naumann, <i>Naturgeschichte der Vögel Mitteleuropas</i> (Natural history of the birds of central Europe) of 1905.
<bdi><a href="https://en.wikipedia.org/wiki/en:Johann_Friedrich_Naumann" class="extiw" title="w:en:Johann Friedrich Naumann"><span title="German ornithologist, engraver and editor (1780-1857)">Johann Friedrich Naumann</span></a>
</bdi>
1903-01-01
Naumann, Natural history of the birds of central Europe, 3rd Ed. Revised by G. Berg et al.; Edited by Carl R. Hennicke. Volume 12, Plate 15. <a rel="nofollow" class="external free" href="https://archive.org/details/mobot31753003759377/page/15/mode/1up">https://archive.org/details/mobot31753003759377/page/15/mode/1up</a>