An internationally important 18th-century shell collection, believed lost for more than 40 years, has been returned to English Heritage after being saved from a skip.

Containing more than 200 specimens, including an extinct species and several believed to have been sent back from Captain Cook's ill-fated third voyage, the collection will go on display at Chesters Roman Fort and Museum for the first time in more than 100 years on 13 March 2024.

A remarkable record of Britain's role in global trade and its colonial reach in the late 18th century, the collection was the lifelong passion of Bridget Atkinson (1732-1814). Despite never leaving Britain and rarely leaving Cumbria, Atkinson had far-reaching connections and amassed more than 1,200 shells from across the globe.

Her passion for collecting was inherited by her grandson, John Clayton (1792-1890) who grew up with Chesters Roman Fort in his garden and whose own archaeological collections form the basis of the museum there.

While most of the shells were sold along with the Clayton estate in 1930, around 200 of Bridget Atkinson's shells remained on display in the museum and were subsequently loaned to the zoology department of Armstrong College, now Newcastle University.

In the 1980s, the shells were thrown out during an office clear-out at the university. Thought lost forever, it has now been revealed that a passing lecturer, Dr John Buchanan, rescued the shells from a skip. Donated to English Heritage by the Buchanan family, the shells have now returned to the museum at Chesters Roman Fort and been reunited with a giant clam that was previously the only remaining piece of the collection.

Dr Frances McIntosh, English Heritage's Collections Curator for Hadrian's Wall and the North East, says, 'We've always known about Bridget Atkinson's collection but had believed it completely lost. To discover that the shells have not only survived but been kept safe and loved all this time is nothing short of a miracle.

'Bridget Atkinson was a remarkable woman, with a real curiosity about the natural world. At a time when women generally collected shells to decorate their furniture and grottos, Bridget was collecting them for their scientific and geographical interest rather than their aesthetics. As well as being a testament to Bridget's character and contacts, this collection is also a superb record of Britain's role in global trade in the late 18th century, not to mention human impact on the natural world.'

Dr Tom White, Principal Curator of non-Insect Invertebrates at the Natural History Museum, who has been helping English Heritage to identify and catalogue the shells, added, 'Bridget Atkinson was one of the earliest known women to have amassed a scientifically significant shell collection from around the world. The collection includes numerous rare species, including New Zealand endemics obtained from her connections to James Cook's third voyage, the extinct Distorsio cancellina and others, like the giant clam, that are now CITES protected.

'These would have been extraordinarily sought-after in 18th-century Britain, during the golden age of shell collecting when single specimens could sell for thousands of pounds.'

The family of Dr John Buchanan says, 'Our father was a marine zoologist and Senior Lecturer from 1958 until his retirement, based at The Dove Marine Laboratory in Cullercoats. He rescued the collection as he believed in conservation, and the shells remained in our family home for 35 years.

'Following the death of our mother, we discovered the shells were part of the Clayton Collection. We were delighted to return the collection to English Heritage for future generations to enjoy.'

Among the shells is a thorny oyster (Spondylus americanus) which, in an 1804 letter, Bridget begged her son Matthew (based in Jamaica) to obtain for her.

'Now my Dear Matthew I have heard that at a place called Cow or Bull Bay I forget which there are the prickly oyster I beg you will send to see if you can get any for me also some good Land crabs in perfect shells and Land shells and a peice (sic) or two small peices (sic) or twigs of the Mangrove oyster and any Scolops (sic) or Muscles if Large or good cockles in pairs.'

Found along the Atlantic coast, from North Carolina down to the Caribbean and as far as Brazil, the thorny oyster is decorated with spiny protuberances around five centimetres long.

Others include a 'Sunburst Star Turban' (Astraea heliotropum), endemic to New Zealand, which was sent to Bridget by George Dixon while he was serving as armourer under Captain Cook during his third voyage on HMS Resolution, and the giant clam Tridacna gigas, the largest bi-valve in the world that is now a CITES protected species.

Another spectacular shell is the chambered nautilus (Nautilus pompilius), which was among the most coveted of natural history items for collectors. The animal that lived inside this shell had around 90 tentacles. It lived in the outer chamber of the shell and, as it grew, it created larger chambers, each time sealing off the vacated one.

• Book to visit the collection (on display from 13 March 2024) at Chesters Roman Fort and Museum in Northumberland here