When I had found Psammonobiotus linearis, I remembered these photomicrographs which I took a year before without paying any attention to the collar. The shells are very small, 14 µm in length, which is nearly half the length of the shells of Psammonobiotus linearis. The second photomicrograph shows a hyaline veil or collar. These shells were found in a sample from Crailoo.
Notice the double nucleolus
Shell 14 µm long