Apports du microscope électronique à balayage dans l'étude des Chitinozoaires opaques

The difficulty of making observations on the opaque Chitinozoa has long been a hindrance to studying them; under the optical microscope they present no more than a silhouette, and the use of incident-light techniques gives little improvement. In contrast, routine use of the scanning electronic microscope (SEM) provides a solution to most of the problems resulting from the opacity of the Chitinozoa.This apparatus makes possible a better knowledge of the morphology and structure of the Chitinozoa (mode of linkage, operculum, internal structure, ornamentation of the test); these are the two essential points for clarifying the hierarchy of the determinant characteristics.In the case of heavily compacted or markedly structured sediments (cleavage, folds), the use of the SEM also allows of establishing the degree of deformation of the Chitinozoa.Lastly, in the field of fine stratigraphic studies, the SEM gives new interest to the opaque Chitinozoa, by making it possible to determine them, and check the identification on published illustrations.A description is given of a preparation procedure which allows of keeping the specimen - after the SEM examination - between the slide and the cover-glass, so that it can be examined later under the optical microscope.