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. The collection is enormously important, especially for researchers working taxonomically with Cenozoic bivalves and gastropods, because Mayer-Eymar established several hundred new species. 

The collection is the property of ETH Zurich, but was on permanent deposit at the Natural History Museum Basel from 1965 to 2020. Since September 2020, the Mayer-Eymar collection has been back at ETH Zurich.