Citrus warburgiana

Citrus warburgiana, the kakamadu or New Guinea wild lime, grows on the south coast of the Papuan Peninsula near Alotau in Papua-New Guinea.
It is a poorly known tree species. It has dark green, spherical fruits about in diameter. It is taxonomically an Australian lime:
This wild lime is a species of Microcitrus according to the Swingle system, called Microcitrus warburgiana, and according to the classification of David Mabberley, it is to be called Citrus warburgiana. It is the only Microcitrus coming from outside Australia. Being native to New Guinea, the closest Microcitrus to it is away, namely Citrus garrawayi.