Abstract: Rare borings attributed to Sedilichnus have been found in crinoids from the Silurian of Estonia. The Rhuddanian Sedilichnus is the earliest symbiotic boring in crinoid columnals of Baltica. These borings presumably were domiciles made by symbiotic organisms. These symbionts presumably had a negative effect on the host crinoid. Symbiotic borings in the Silurian of Estonia may have been less common than similar traces in the Silurian of nearby Gotland. Olev Vinn,Mark A. Wilson, William I. Ausich & Ursula Toom