Freshwater Algae of North America Class Zygnematophyceae C.Hoek, D.G.Mann & H.M. Jahns (1995), nom. inval. - conjugating green algae see Class Zygnematophyceae Round ex Guiry (2013) Order Desmidiales - placoderm desmids Family Desmidiaceae Kützing ex Ralfs (1845) Genus Pleurotaenium Nägeli (1849) 1 Pleurotaenium trabecula (Ehrenb.) ex Nägeli (1849) 2 Pleurotaenium ehrenbergii (Ralfs) de Bary (1858)