Hederella is an epibont which is a non parasitic organism growing upon another animal, most often a shell. It is a genera of Bryozoan within the Cyclostomata order and has at least 12 species within the Silica shale according to the 1975 book by Robert V. Kesling & Ruth B. Chilman: Strata and Megafossils of the Middle Devonian Silica Formation: Museum of Paleontology, Papers on Paleontology, No. 8, pg. 58, 61.
As I've mentioned before, trying to ID down to species level in Bryozoans is difficult so for now I am just going to associate them with their genera name, Hederella.
Some winding colonies on Strophodonta shells
The host shell for this colony is Megastrophia
Hederella is an eye catching epibont forming colonies that look to me like detail stitching in a quilt. When I find a shell with them growing on it I'm more likely to toss it into my collecting bag because of the interesting look.
Here are some closeups I took with my Zorb digital microscope.