the Volga Region

Terminal layers of carbonate rocks of Maastrichtian and lower intervals of Paleocene aleurite-pelitic formations are accessible for investigation in Krasny Oktyabr and Bolshevik quarries (Volsk Depression). In the bottom of the Paleocene accumulation of skeletons of calcareous and siliceous sponges has been confirmed, mollusk and elasmobranch assemblage has been determined.

Among the numerous and diversiform Late Cretaceous siliceous sponges collected throughout the Volga region, several representatives of the genus Botryosella have been encountered, previously unknown for the area. Analysis of the skeleton morphology, peculiar for massive transverse outgrowths, confirms manifestations of isomorphism in Hexactinellids and the opinion of inaccuracies available in the descriptive terminology applied to the skeletal morphology of this Porifera group.