Mary was the Duchess of Ancaster, married to Peregrine Bertie, Duke of Ancaster. They had six children together.
Reference:
William Stukeley to Hans Sloane, 1735-07-04, Sloane MS 4054, f. 64, British Library, London
Peregrine Bertie, 3rd Duke of Ancaster and Kesteven, Wikipedia, [https://en.wikipedia.org/wiki/Peregrine_Bertie,_3rd_Duke_of_Ancaster_and_Kesteven, accessed 30/08/2017]
Dates: to
Occupation: Unknown
Relationship to Sloane: Virtual International Authority File: