In January 1904 Percy E. Raymond was appointed Assistant Curator in the section of Paleontology – Division of Fossil Invertebrates at Carnegie Museum, by then-Director W. J. Holland. Upon arriving, Raymond began unpacking and organizing the thousands of fossils of the de Bayet collection, a chore that is continued by section staff to this very day. Raymond also started learning about the regional geology of western Pennsylvania and making additional collections. These efforts were in keeping with the emphasis of most paleontologists of that day. Raymond collaborated with Earl Douglass (of Carnegie dinosaur fame) during one of the museum's early field collecting expedit­ions to Minnesota and Montana. Raymond continued to build new collections, curate the de Bayet collection, conduct research, and develop educational programs until 1910 when his request for a raise was denied. He left Carnegie Museum and soon found his way to Harvard’s Museum of Comparative Anatomy, where he became one of the most well-known and respected paleontologists of his day. Raymond never forgot his Carnegie Museum roots and continued to contribute valuable fossil collections from such important formations as the Burgess Shale and the Mazon Creek Shale.

The position Raymond vacated remained open until 1922. During that time, the section’s collections were enlarged via the acquisition of 12,500 specimens from the H. H. White collection.