This study about a bored crinoid is in fact about a peculiar bored crinoid:
“A peculiar bored crinoid from Salthill Quarry, Clitheroe, Lancashire (Mississippian; Tournaisian), UK,” S. K. Donovan and A. Tenny, Proceedings of the Yorkshire Geological Society, epub November 11, 2015. The authors, at Naturalis Biodiversity Center, Leiden, the Netherlands, and at the town of Rochdale, Lancashire, UK, report:
“The infestation of the live crinoid must be considered ectoparasitic.”
(Thanks to Tom Gill for bringing this to our attention.)