In her career, Duncan gained a distinguished reputation for her work on fossil corals and Bryozoa.

Similar fossil corals occur in a variety of locations, however the name Petoskey stone should only be applied to those from Northern Michigan.

G. wardi and other similar fossil corals may even have been able to move along the sea floor or right themselves if tipped over.

In addition to papers on fossil corals, he dealt with some of the living forms, also with the Echinoidea and other groups, recent and fossil.

Stromatolites turned out to be a kind of fossil coral found in Australia that preserves records of the tides from hundreds of millions of years ago.

A black limestone containing fossil corals of the Carboniferous Period, some 325 million years ago.

Like Maré and Ouvéa, the other Loyalty islands, Lifou is made of fossil coral.

The Petoskey stone, which is made of fossil coral, is the state stone of Michigan.

Bunaken Island also has volcanic origins with a significant amount of uplifted fossil coral.

In addition, they produced further support from the unlikely domain of the study of fossil corals in the Pacific.