Frontispiece 1. Spondylus Americanus. (Young.) 2. Nautilus pompilius. (Young.)
<a href="https://en.wikipedia.org/wiki/George_Brettingham_Sowerby_II" class="extiw" title="w:George Brettingham Sowerby II">George Brettingham Sowerby II</a>, (1812–1884)
<a rel="nofollow" class="external text" href="https://www.gutenberg.org/ebooks/43417">'<b>A Conchological Manual'</b></a>, available freely at <a href="https://en.wikipedia.org/wiki/Project_Gutenberg" class="extiw" title="w:Project Gutenberg">Project Gutenberg</a>