Abstract
Microscope slides containing material from Sierra Leone used by Woodhead and Tweed to describe eight new Surirellaceae taxa in the mid-twentieth century were reinvestigated. Only two taxa were found on the original slides, Surirella approximata Woodhead & Tweed and S. engleri [var. constricta] f. minor Woodhead & Tweed. The valve variability of S. engleri O. Müller includes valves of S. engleri [var. constricta] f. minor which is now regarded as a synonym. As no holotypes were indicated by the authors, types are given here. Comments on S. rudis var. sierra-leonensis Woodhead & Tweed, S. rudis [var. sierra-leonensis] f. constricta Woodhead & Tweed and S. esamangensis Foged are also given. Valves resembling Stenopterobia recta Woodhead & Tweed, Surirella asperrima f. rokuprensis Woodhead & Tweed, S. engleri f. sierra-leonensis Woodhead & Tweed and S. rokuprensis Woodhead & Tweed could not be found on the Woodhead and Tweed original slides.
Acknowledgements
The authors wish to thank the Andrew Mellon Foundation for funding the ‘Pilot project on the digitization of African micro-algae types and typical specimens: the diatom family Surirellaceae’ and for valuable comments made by the referees and editors.