That is seanchló, the old Irish font. The inscription also uses older spellings and word forms that were used before the language was standardised.
Go ndéanaidh croidhe ro-naomhtha Íosa trócaire ar anamaibh Enrí Uí Luain a fuair bás 2adh lá Aibreáin 1901. Agus Sibéil Ní Chiardha a bhean phósda a fuair bás an 26adh lá Márta 1901. Agus ar anam a mic Enrí Óig Uí Luain M.E. fear dligheadh a fuair bás 27adh Iúil 1898. Agus ar anam an t-athair Dhómhnaill Uí Luain D.D. an mac is sine a fuair bás 15adh Samhin 1911. A bhí ina ollamh i gcolaite Muighe Nuadhat ar feadh cúig bliadhna déag agus ar anam an t-athair Cathal Uí Luain, S.P. a chuir suas an leac-uaighe seo agus a fuair bás ar 30adh Deireadh Fóghmhair 1935.
May the sacred heart of Jesus have mercy on the souls of Enrí Ó Luain, who died 2nd day of April 1901. And Sibéil Ní Chiardha, his wife, who died the 26th day of March 1901. And on the soul of their son Enrí Junior Ó Luain M.E. a lawyer, who died 27th of July 1898. And on the soul of Father Dómhnall Ó Luain D.D., the oldest son, who died 15th November 1911, who was a professor in Maynooth college for fifteen years and on the soul of Father Cathal Ó Luain, S.P. (= sagart paróiste, parish priest) who put up this gravestone and who died on 30th October 1935.
I'm afraid I don't know what the initialisms M.E. and D.D. stand for, sorry!