Illustration from Diatomaceae of Philadelphia and Vicinity. <i>Rhopalodia gibba</i> (Kuetz.) Mueller
Charles Sumner Boyer (1856-1928).
1916
Extracted fig. 23 from <a href="//commons.wikimedia.org/wiki/File:Diatomaceae_of_Philadelphia_Plate_31.jpg" title="File:Diatomaceae of Philadelphia Plate 31.jpg">File:Diatomaceae of Philadelphia Plate 31.jpg</a>, source: <a rel="nofollow" class="external free" href="https://archive.org/details/diatomaceofphi00boye">https://archive.org/details/diatomaceofphi00boye</a> Illustration from Diatomaceae of Philadelphia and Vicinity, Plate 31