The collection of Karl Mayer-Eymar encompasses 150 years of mollusc research in Switzerland and includes around 350,000 mussels and snails.

From around 1845 until his death in 1907, Karl Mayer-Eymar, also known as 'Tertiary Mayer', collected molluscs from the Tertiary period in Europe and North Africa.

The collection, which is grouped according to criteria of systematics, stratigraphy, location and doublets, is an impressive example of a scientist's work. In his lifetime, he collected whatever he could. Only a small proportion of it has been processed and published. Future generations are able to view these bequeathed treasures and integrate them into their own research.

Stored at the ETH Zürich for over a century, the entire Mayer-Eymar collection, including numerous holotypes and original figures, was transferred as a permanent holding to the Natural History Museum Basel at the start of the 1970s.