Die Unterfamilie Chasmopinae (Trilobita, Pterygometopidae) aus baltoskandischen Geschieben sowie Baltoskandia und angrenzenden Gebieten

Within more than 50 years the author has collected a vast number of trilobites originating from erratic boulders of Ordovician age, among them many specimens of the subfamily of Chasmopinae. By keeping all fossils from the distinct boulder it was possible to classify nearly all species stratigraphically.

Out of the middle- to high-ordovician family of Pterygometopidae altogether eight genera of Chasmopinae are dealt with. These may be split up into two groups: One group comprising five genera with a so-called locking system (vincular furrow) and the second one consisting of three genera without such a locking system.

Altogether 53 species of Baltoscandian provenience, including 11 species new to science [Scopelochasmops mukranensis n. sp., Scopelochasmops praewrangeli n. sp., Bolbochasmops kaskovoensis n. sp., Toxochasmops (Toxochasmops) praewesenbergensis n. sp., Toxochasmops (Toxochasmops) luebzensis n. sp., Valdariops vierradensis n. sp., Valdariops scheffelae n. sp., Valdariops schneideri n. sp., Valdariops ruegensis n. sp., Valdariops postnybyensis n. sp., Valdariops porkuniensis n. sp.], are characterized and differentiated from each other. Additionally, five species from Great Britain and one from Canada are discussed and correlated with those from Baltoscandia. To differentiate the species from each other, distinctions at the cephalon and pygidium are taken into consideration, revealing on the other hand, evolutionary trends.

In more than half the number of species dealt with, the author succeeded in clearing the hypostome in its original position from the embedding limestone or matrix. This preparational work has made it possible to see pores, to study the shape of tubercles and the gestalt of the eyes. The different types of limestones are characterised and described.