Phylum: Charophyta   Family: Desmidiaceae

Cosmarium crenatoides P.F.M. Coesel & A. van Geest 2022

Until recently this was better known as Cosmarium costatum var. gutwinskii Croasdale (1956). Croasdale (l.c.: 26, pl. 15: 24) suggests a series of 12 granular lines above the isthmus, but later finds give 7-8, and has shed more light on its cell structure suggesting it has little affinity with Cosmarium costatum. A rare taxon which probably has an Arctic-alpine distribution. Found in ephemeral pools and shallow depressions.

References: 
Coesel, P. & Van Geest, A. (2022) Two taxonomically confusing Cosmarium species from ephemeral puddles newly described.
Croasdale, H.T. (1956). Freshwater algae of Alaska I. Some desmids from the Interior. Part 2: Actinotaenium, Micrasterias and Cosmarium.
Kouwets, F.A.C. (in manuscript) European Flora of the Desmid Genus Cosmarium.