A new Alga for me...

Now that we're in the depths of winter I have little of waterborne interest to investigate. I do have a few water containers sitting in a basement window sill that have some algae from my aquarium growing in them. This afternoon I noticed a new growth on the glass side of one bowl and managed to scrape a bit off to view under the microscope. It turned out the specimen was a radial, flattened and multicellular alga that I had never seen before. I'll try to find out what it is but until I do here are a few images I took at various magnifications. After a bit of sleuthing it looks like its a member of the genus Coleochaete , possible orbicularis.

 Here it is at 40X. It appears to have grown out from a central cell and has retained a fairly symmetrical appearance.

This image has been cropped from a 100X magnification photo. The symmetrical growth is very evident here.

Here is a final image with a magnification of 400X. A scale bar indicates the cells are from 15 to 20 microns long.