 State Geologist Eugene Allen Smith encouraged Aldrich to concentrate his efforts in the Tertiary paleontology of the Coastal Plain, often sending him material to identify, and Aldrich collected thousands of fossils from now-classic sites along the Alabama and Tombigbee Rivers, such as Claiborne.He contributed an article to Bulletin 1 of the Geological Survey of Alabama on the state's Eocene fossil record, including nine plates illustrating new species.His collection of modern shells is now in the Florida Museum of Natural History in Gainesville, and his fossil shells are in the Geological Survey of Alabama Paleontological Collection and the Alabama Museum of Natural History.