The type collection of amphibians comprises specimens found worldwide, with the majority having been collected between the end of the 19th and start of the 20th century. The specimens come largely from expeditions and collection trips undertaken by the Natural History Museum Basel.
Larger series come from New Caledonia, India, Sri Lanka (formerly Ceylon), and Sulawesi (formerly Celebes). Alongside various individual specimens, there are also smaller type series. These come from Venezuela, Guatemala, the former Gulf Coast, Madagascar, West, East and South Africa, the Philippines, Indonesia, South America, and from the Bhutan expedition of the Natural History Museum Basel in 1972.
Many of the over 100 taxa in the type collection were described by George Albert Boulanger. He worked as a research assistant at the Natural History Museum in London from 1880 to 1920.