Mag. 400x
Image 1 = Specimen 1
Image 2 (composite) = Specimen 2
Image 3 (composite) = Specimen 3
I think this Staurastrum has 4 arms per semicell and robust ornamentation; first specie I've encountered with arms pointing toward the isthmus. The following seems to be an exact match, but a species is not given (and it was the only similar Staurastrum I could find): http://protist.i.hosei.ac.jp/PDB/Images/Chlorophyta/Staurastrum/Eustaurastrum/Processiformes/4_arms/Staurastrum_3d.html. (What do you think @geraldojpr?) - Found a specimen presenting an apical view; added a 4th image.
A pond edge water sample (freshwater) was taken on 10/19/2021 using a 10 micron dip net to enrich for microorganisms.