Both Semiorbis rotundus and S. hemicyclus have larger, even more strongly arched valves.
Semiorbis catillifera has sub-rostrate apicies, and less valve curvature.
Semiorbis hemicyclus
has valves that are slightly less curved and less protracted.
Diatoms of North America is running a fundraising campaign to keep the servers in operation. We need you to reach our $25,000 fundraising goal.
If you use and appreciate DONA, make your DONAtion today.
For the Gift Designation, type "diatom" in the search box and select "Diatom Lab Research Fund". This is the designated fund for diatoms.org.