The organic linings of minute foraminifers can be naturally stained by Fe-oxides during early diagenesis. This protects them against destruction and make them visible in thin sections. Up till now the microforaminiferal linings were described only from extractions for palynological investigation. A set of morphotypes of the foraminiferal linings from thin sections of Callovian-Oxfordian limestones and Lower Cretaceous cherts is illustrated with comments. The morphological aspects of the foraminiferal linings allow us to associate them into morphogroups and form genera. Some of well-developed linings are sufficient for their generic as well as subgeneric classification enclosing more than 30 foraminiferal taxa. The reasons for the organic-walled structure of “microforaminifers“ are inferred in environmental stress or dissolution of rigid tests after death. The possibility of using some linings in foraminiferal stratigraphy is discussed.