Thomas Shimmin married Ann Cowley Aug.1 1835 in the parish of Patrick. According to IGI they had 4 children , Elinor 1835, Elinor 1837, Philip 1839 and Ann 1842. It seems Elinor1835 and Philip 1839 died young.

In the USA it looks like Thomas died and Ann remarried to Thomas Holland 1865 then she died 1876 with name Ann Shimmin Holland.

There is a picture of her headstone also in 'Find a Grave' site.

The details on both headstones are very similar to your information but there may be coincidences.

Len Faragher