Both Diatoma liber and Diatoma interstitiale are cited in Kützing (1844, 1849) as synonyms of his Biddulphia quinquelocularis Kützing (Kützing, p. 138, pl. 19, fig. I, 1, 2, see Fig. 7; ‘ Biddulphia quinquelobata’ was an alternative name used only for herbarium material). Although described as new, Kützing included a number of apparent synonyms (Table 2) as well as numerous localities (Table 3, marked with Y in the last column). Most subsequent commentators have considered Biddulphia quinquelocularis a synonym of Biddulphia biddulphiana (J.E. Smith) Boyer (1900, p. 694).

The Kinker catalogue lists six slides (* in Table 3) for quinquelocularis along with one addition slide for the invalidly published ‘ Biddulphia elongata ’ Meneghini (in Kützing 1849, p. 137, BM 19394), also considered a synonym of B. quinquelocularis. Although the Canary Islands are listed in Kützing (1844), no slide has Biddulphia quinquelocularis indicated as present. ‘Kützing 821’ is the source material for BM 19392, the apparent type material for B. quinquelocularis (Figs 8–10).

1 On the slide label: “Genoa 1828”

2 No coverslip or specimens

3 Given as 937 in error.

4 W has specimens from ‘Kützing 936’ (W0088953), not present in BM. These are specimens of Biddulphia quinquelocularis from Dalmatia, Croatia. They have not been examined.

5 https://websites.rbge.org.uk/algae/collections/ Biddulphia _WalkerArnott_Foreign_1.jpg

‘ Biddulphia elongata ’ Meneghini has only been recorded by Kützing (1849, p. 137) but Meneghini did comment earlier on the specimens: “Abbiamo nell’Adriatico le due specie quinquelocularis e trilocularis. Lo riferisco alla seconda una forma a bacilli minori e molto allungati, che credevo dapprima una nuova specie e come tale comunicai al Kützing, il quale la credette invece appartenente alla quinquelocularis ” (Meneghini 1846, p. 1998). ‘Kützing 927’ is the source material for BM 19394, the apparent type material for ‘ B. elongata ’, which contains just fragments, mostly with fragments of a species of Rhabdonema (Figures 11, 12, BM001167211: https://data.nhm.ac.uk/dataset/collection-specimens/resource/05ff2255-c38a-40c9-b657-4ccb55ab2feb/record/8288389).