Achnanthes brevipes var. brevipes Agardh, 1824 (original description)
Achnanthes longipes var. longipes Agardh, 1824 (original description)
Batrachospermum durum C.Agardh, 1824 accepted as Batrachospermum gelatinosum (Linnaeus) De Candolle, 1801 (original description)
Calcothrix ramulosa Desvaux ex Agardh, 1824 (original description)
Ceramium intricatum C.Agardh, 1824 accepted as Spermothamnion intricatum (C.Agardh) De Toni, 1903 (original description)
Conferva aegagropila var. adnata Agardh, 1824 accepted as Cladophora aegagropila (Linnaeus) Trevisan, 1845 accepted as Aegagropila linnaei Kützing, 1843 accepted as Aegagropila brownii (Dillwyn) Kützing, 1854 (original description)
Conferva caerulea Balbis ex C.Agardh, 1824 accepted as Compsopogon caeruleus (Balbis ex C.Agardh) Montagne, 1846 (original description)
Dasya C.Agardh, 1824 (original description)
Diatoma biddulphianum (J.E. Smith) Agardh, 1824 (new combination reference)
Diatoma crystallinum C.A. Agardh, 1824 (original description)
Diatoma elongatum (Lyngbye) C.A. Agardh, 1824 accepted as Diatoma tenue var. elongatum Lyngbye, 1819 (new combination reference)
Diatoma fasciatum (Lyngbye) Agardh, 1824 accepted as Fragilaria fasciata Lyngbye, 1819 (new combination reference)
Diatoma latruncularium (Lyngbye) Agardh, 1824 accepted as Fragilaria latruncularia Lyngbye, 1819 (new combination reference)
Diatoma lyngbyei Agardh, 1824 (original description)
Diatoma tenue C. Agardh, 1812 (original description)
Diatoma unipunctatum (Lyngbye) Agardh, 1824 accepted as Fragilaria unipunctata Lyngbye, 1819 (new combination reference)
Diatoma vesiculosum Agardh, 1824 (original description)
Frustulia C.A. Agardh, 1824 (original description)
Frustulia acuta (Lyngbye) Agardh, 1824 (new combination reference)
Frustulia cuneata (Lyngbye) Agardh, 1824 (new combination reference)
Frustulia elliptica C.Agardh, 1824 (original description)
Frustulia minor Agardh, 1824 (original description)
Frustulia obtusa (Lyngbye) C.Agardh, 1824 (original description)
Frustulia parasitica Agardh, 1824 (original description)
Frustulia viridis C. Agardh, 1829 (original description)
Gomphonema geminatum f. geminatum (Lyngbye) Agardh, 1824 (new combination reference)
Gomphonema paradoxum Agardh, 1824 (original description)
Hutchinsia breviarticulata C.Agardh, 1824 accepted as Polysiphonia breviarticulata (C.Agardh) Zanardini, 1840 (original description)
Hutchinsia foeniculacea C.Agardh, 1824 accepted as Polysiphonia foeniculacea (C.Agardh) Sprengel, 1827 (original description)
Hutchinsia macrocarpa C.Agardh, 1824 accepted as Polysiphonia macrocarpa (C.Agardh) Sprengel, 1827 (original description)
Melosira C.A. Agardh, 1824 (original description)
Melosira discigera Agardh, 1824 (original description)
Melosira juergensii var. juergensii Agardh, 1824 (original description)
Melosira lineata var. lineata (Dillwyn) Agardh, 1824 (new combination reference)
Melosira moniliformis f. moniliformis (O. F. Muller) Agardh, 1824 (new combination reference)
Melosira nummuloides var. nummuloides (Dillwyn) Agardh, 1824 (new combination reference)
Meridion C.A. Agardh, 1824 (original description)
Meridion ovatum Agardh, 1824 (original description)
Meridion radians Agardh, 1824 (original description)
Meridion vernale C.Agardh, 1824 (original description)
Schizonema C.A. Agardh, 1824 (original description)
Schizonema apiculatum var. apiculatum Agardh, 1824 (original description)
Schizonema corymbosum var. corymbosum Agardh, 1824 (original description)
Schizonema dillwynii var. dillwynii Agardh, 1824 (original description)
Schizonema grateloupii Agardh, 1824 (original description)
Schizonema lacustre C.Agardh, 1824 (original description)
Schizonema micans Agardh, 1824 (original description)
Schizonema quadripunctatum (Lyngbye) Agardh, 1824 (new combination reference)
Schizonema ramosissimum f. ramosissimum Agardh, 1824 (original description)
Schizonema rutilans var. rutilans (Trentepohl ex Roth) Agardh, 1824 (new combination reference)
Schizonema smithii var. smithii Agardh, 1824 (original description)
Solenia C.Agardh, 1824 (original description)
Solenia attenuata C.Agardh, 1824 accepted as Ulva attenuata (C.Agardh) Naccari, 1828 (original description)
Thaumasia C. Agardh, 1824 (original description)
Thaumasia ovalis C.Agardh, 1824 (original description)