This Staurastrum species forms a chain of cells after cell division. They are not firmly attached. If you press the coverslip of your sample they will detach.
The genus Staurastrum is problematic. Sometimes it is difficult to decide if a species belongs to this genus or not. Similarly, it is hard to distinguish some species from Xanthidium.
Xanthidium is basically bi-radial. Staurastrum is polyradial. In this species each arm points into 3 directions: tri-radial.
