Calendars of Wills and Administrations 1858-1920 National Archives of Ireland www.willcalendars.nationalarchives.ie/search/cwa/home.jsp
You may need to try various spellings of the surname when searching.
If he had property or assets in Britain as well as Ireland, Richard's will may be there.
This about Richard McGillycuddy from The Peerage website www.thepeerage.com/p50393.htm
Richard McGillycuddy, The McGillycuddy of the Reeks 1790-1866. Son of Francis McGillycuddy & Catherine Mahoney. Grandson of Cornelius McGillycuddy & Catherine Shute.
"Boetius" is an unusual first name. Is it a nickname or short for an other name?
Cornelius McGillycuddy had a son, Eusebius who himself had a son called Eusebius, according to "The Peerage" website.
Have you located newspaper obituaries about the death?