1. Diatoma liber Suhr 1831, p. 686 (1834, 17 (1), tab. III, fig. 4, reproduced here as Figure 1) (Figures 2–6) Described in the first ‘Beschreibung einiger neuen algen’ series from Canary Island specimens (“Kanarische Inseln”), Suhr provided a fairly detailed account of Diatoma liber (Suhr 1831, p. 686) publishing a series of figures in a later edition of Flora oder Botanische Zeitung (Suhr 1834, 17 (1), tab. III, fig. 4, see Fig. 1). Diatoma liber has been assumed by many to be the same species as Diatoma interstitiale Agardh (1832, p. 54), both having been described from Suhr’s Canary Island material (Agardh 1832, p. 54, “ Sphaerococcus Corneum investiens ad insulas Canariensis. Specimen misit v. Suhr”; Kützing 1833, p. 585, “An Sphaerococcus corneus, von den canarischen Inseln, v. Suhr”; see also Montagne in Barker-Webb & Berthelot 1840, p. 193, “Gelidio corneo parasitantem hancce speciem mihi ignotam invenit cl. Suhr, qui cum celeb. Agardhio specimen communicavit.”; and their footnote: “J’omets à dessein le Diatoma liber Suhr, originaire aussi des Canaries, selon cet auteur, par la raison que ses caractères ne m’ont pas paru assez solides pour lever tous mes doutes sur sa légitimité”). Two slides in the BM Kützing collection are made from Canary Island material (“Ins Canar.”) and both said to have specimens of Diatoma liber. The same two slides are catalogued for Diatoma interstitiale (Table 1) 1 When numbers are double-underlined in Eulenstein’s Catalogue it indicates that ‘Kützing 823’ (BM 19390 “Ins Canar.”) was the source of the original material for Biddulphia septemlocularis (See Cox 1995). The Eulenstein catalogue of Kützing’s BM collection (Eulenstein 1868) notes that for ‘Kützing 766’ it includes specimens of: “ Diat. interstitiale Ag. (Diatoma liber Suhr?) Ins Canar. bei Grammath. Marina ” (italics not in original) and for ‘Kützing 823’ specimens of: “ Bidd. septemlocularis Kg. [Isth. ernerva [= I. enervis] ... canariensis Kg] Diat. interstitiale K. … liber Suhr Ins Canar. Kütz. ” 4 (italic not in original). The implication is that all these names (except those in Isthmia) refer to the same specimens. Diatoma liber has been written as Diatoma liberum (Kützing 1849, p. 137), as ‘ Diatoma liberum Agardh’ (e.g., de Toni 1894, p. 870, Boyer 1901, p. 694 as a synonym of Biddulphia biddulphiana) and as ‘ Diatoma linerum Agardh’ (in Mills 1933, p. 282, under Biddulphia biddulphiana) 5. These all refer to the same taxon.

Published as part of Williams, David M., 2021, Studies on type material from Kützing's diatom collection VI: The identity of Diatoma liber Suhr (1831), pp. 215-223 in Phytotaxa 528 (3) on pages 215-217, DOI: 10.11646/phytotaxa.528.3.6, http://zenodo.org/record/5788164