The title of Earl of Narmanton was created in 1806 for a Charles Agar.This title has, as far as I know nothing to do withe the Eagars or Agars in question.The Eagars came to Ireland in 1560 and to Co. Kerry in 1650.There were four brances of the family and the one dealing with James Walter Eagar or Agar is the 1st branch.The name wasn't officially changed at any stage.Its just a spelling error.James Walter married a Susan Shelton from Rossmore House in Co. Limerick and hence the name Shelton Agar.
John Shelton Agar was born the 23rd Oct 1842 and died in China on the 6th Sept 1902, leaving 13 children, Gus being the youngest. The memorial in Kandy is to him.
As regards Mary Agar,I have a date of a daughter born to Walter James Agar & Barbara Finlay on the 28th March 1875 at Mahonville Estate, Ceylon,the sister of Walter, Roper and Annie etc,but the child was not named in the newspaper,so it is possibly Mary.Are you sure about the other 2 sons Robert Charles and Edward Lethbridge?
If you would like any further information, please feel free to come back to me.