Crinoid stems from the Silurian of Gotland and the Devonian of Morocco show a variety of the malformations which in the literature since 1884 have been almost invariably ascribed to myzostomid activity. No observations support this theory; except for possible cysts in the Moroccan material, the stems are massive with shallow pits in a superficial layer of calcium carbonate. Attached Foraminifera with agglutinated siliceous tests show a remarkable association with these pits. Cornulitids were responsible for other malformations. If the few cases of. previously described cysts on the stems were asSociated with myzostomids, the latter would have represented adaptations very different from those in Recent forms.