Speaking of paleontology

Thin-walled tubular fossils

Here are a couple of thin-section photomicrographs, with scales, of some encrusting and possibly boring fossils. The thin and irregular white walls are made of calcite. These look sort of like worm tubes, except they are smaller than most worm tubes and have a much simpler structure than most worm tubes. If you know anything about them, please let me know.