"- You said, Stephen answered, O, it's only Dedalus whose mother is beastly dead.
A flush which made him seem younger and more engaging rose to Buck Mulligan's cheek.
- Did I say that? he asked. Well? What harm is that?
He shook his constraint from him nervously.
-And what is death, he asked, your mother's or yours or my own? You saw only your mother die." (U1.198)

'Beastly dead' may be an inversion of the common Irish expression 'beo beithioch', Irish for 'beastly alive.' [suggested by Michael Reidy, a visitor to the site]