Tetracyclus Ralfs, 1843
Holotype species: Tetracyclus lacustris Ralfs
Original publication and holotype designation: Ralfs, J. (1843). On the Diatomaceae. Annals and Magazine of Natural History 12: 104-111, 1 p. [pl. 2].
Request PDFDescription: Frustules rectangular in girdle view, when mature the pervalvar axis exceeding the apical axis. Valves isopolar, their surface flat, the mantle vertical, the margin a sharply stepped-out hyaline lip. Primary internal transapical ribs present, and sometimes secondary and tertiary ribs also. Axial area longitudinal with indefinite margins, sometimes internally thickened to form a sternum. Striae parallel to slightly radiate extending across the mantle as far as the projecting hyaline valve margin. Virgae much coarser than the small vimines and raised above the valve surface close to the margin, become less so towards the axial area. Areolae close to the axial area more widely spaced than elsewhere and somewhat irregularly distributed. Apical pore fields present, consisting of an area where the striae are as closely spaced as the areolae within them. Rimoportulae usually present, varying in number and position. Cingulum consisting of several open bands, their openings at alternate poles. The bands of four kinds: valvocopula bearing a septum; primary copulae each~with a ligula and a septum; secondary copulae without septa their ligulae larger than those of the primary copulae; a single pleura. Septa arising from the abvalvar part of the pars exterior of the valvocopula and the primary copulae, extending variable distances into the frustule, with a pore close to the base on the abvalvar face communicating with a group of pores on the outer face of the band.
Information contributed by: Williams (1987). The most recent alteration to this page was made on 2017-11-24 by M.D. Guiry.
Taxonomic status: This name is of an entity that is currently accepted taxonomically.
Gender: This genus name is currently treated as masculine.
Most recent taxonomic treatment adopted: Williams, D.M. (1987). Observations on the genus Tetracyclus Ralfs (Bacillariophyta) I. Valve and girdle structure of the extant species. British Phycological Journal 22: 383-399.
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Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera,
organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA)
and intended to be published in CD format.
These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above.
The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.
Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.
Linking to this page: https://www.algaebase.org/search/genus/detail/?genus_id=44214
Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 24 November 2017. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 19 April 2024
