Curator Of Mollusks, Elizabeth Shea

The Museum’s mollusk collection is the tenth largest in the United States, according to a study published in the December 2018 edition of the American Malacological Bulletin.

Curator of Mollusks Elizabeth Shea, Ph.D. co-authored the paper with colleagues from the Field Museum of Natural History and the Academy of Natural Sciences of Philadelphia. Mobilizing mollusks: Status update on mollusk collections in the U.S.A. and Canada, updates research from 1975 about museum mollusk collections. Surveys were sent to 86 organizations to determine which museums had the largest collections. The paper’s authors estimate there are 8.5 million lots (or grouping of shells from the same species, collected at the same time and location), resulting in 100 million specimens at about 90 institutions. Seventy-nine collections are included in the paper.

Natural history collections play an important role in our understanding of biodiversity, evolution, population genetics, environmental impacts, and more. The DMNH mollusk collection includes 220,000 catalogued lots, or 2 million mollusks, representing more than 18,000 species. The collection is worldwide in scope, covering all seven living classes of mollusks. 

Collections Manager, Alex Kittle

Work on the study began in 2017 at a workshop during the American Malacological Conference in Newark, Delaware, when Shea was the organization’s president. “The process took over two years to distill information into what is now a 40 page paper,” Shea said. This paper also set standards for determining what constitutes very small, small, medium and large collections. In 1975, DMNH had a medium sized collection, with 70,650 cataloged lots. Currently, with more than 220,000 cataloged lots, DMNH’s collection is considered large and compares with many of the top natural history museums in the United States.  

Collections management is changing with the growing use of technology. The mollusk department at DMNH is digitizing the collections through a grant from InvertEBase, a online catalog of specimens. Georeferencing, which is adding coordinates of where the specimen was found, is a new addition to digitization. “We want to make our collection data more available to the whole world,” Shea says. In the last four years, about 25 percent of DMNH’s mollusk collection has been digitized. 

InvertEBase can be accessed by anyone, and users are free to browse through the collection’s digital data. 

Scientific Mollusk Collections in North America

10 Largest Collections: More than 160,000 lots

7 Medium-Large Collections: Between 76,000-159,999 lots

10 Medium Collections: 30,000-75,999 lots

20 Small Collections: 9,000-29,000 lots

32 Very Small Collections: Less than 9,000 lots

Top Ten Collections By Number Of Cataloged Lots

  1. National Museum of Natural History (1,081000)
  2. Academy of Natural Sciences (501,000)
  3. The National History Museum of Los Angeles County (500,000)
  4. University of Florida Museum of Natural History (497,459)
  5. Field Museum of Natural History (382,000)
  6. Museum of Comparative Zoology, Harvard University (372,056)
  7. American Museum of Natural History (319,000)
  8. Bernice P.Bishop Museum in Hawaii (300,000)
  9. University of Michigan Museum of Zoology (251,000)
  10. Delaware Museum of Natural History (220,287)

2 million mollusks

The DMNH mollusk collection includes 220,000 catalogued lots, or 2 million mollusks, representing more than 18,000 species. The collection is worldwide in scope, covering all seven living classes of mollusks described below. Gastropods comprise 75 percent and bivalves comprise 20 percent of the collection, with the remaining five percent including the other five classes. Most specimens are recent; however, there is some Cenozoic fossil material.


The largest and most diverse group of mollusks is gastropoda, or slugs and snails. They are also great indicators as to the health of an ecosystem, as they are the most susceptible to changing environmental pressures.

Bivalvia (clams, mussels, oysters)

Possibly the most important group to our own region in terms of economics and the health of our aquatic ecosystems. As efforts are underway around the region to restore the fisheries and waterways, the Museum’s historic records of the bivalves that occurred in the area provide conservationists a glimpse of the fauna once found in the state’s streams, bays, and coastline.

Polyplacophora (chitons)

Chitons are a unique class of mollusks that have eight armor plates, instead of the singular shell of snails or two shells of clams.  The armor plates protect the animal that has a large muscular foot that attaches to hard surfaces, usually rocks, along the coastline.  The chiton will slowly move across the rock rasping algae off to eat.


These mollusks are tooth or tusk shaped. They live in sediment offshore. There are four genera of tusk shells (Dentalium is typical and most common) and more than 350 species.

Cephalopoda (octopods + squids)

This is group contains some of the largest, most mobile, and most intelligent mollusks. They also have a long fossil history and include the belemnite, the Delaware state fossil.


These tiny single shell animals were only known as fossils until 1952 when a live monoplacophoran was discovered more than 11,000 feet deep off the coast of Costa Rica.


Known as the naked mollusks, they lack shells, and can be found in oceans all over the world in very deep water.