Hello Anne, 
The large number mentioned by nenny4 weren't there at the time of the Valuation in Co. Donegal in 1857. The extracts show one in Tyrone and three in Donegal ... two of them are called William. There were no others in Ireland so I'd suggest concentrating the search in Donegal. 
William Crumlish, Town Parks of Strabane, Camus, Tyrone 
William Crumlish, Monclink, Raymoghy, Donegal 
Daniel Crumlish,  Gortnaskea, Fahan Upper, Donegal 
John Crumlish,    Drummay, All Saints, Donegal 
Have you contacted Martin McMenamin who is searching for the 
 Crumlish family in Ireland  on Genforum. His ancestors lived at Gortnaskea and Monreagh in the Parish of Upper Fahan, Inishowen Co. Donegal. 
Chris