James Mooney born 1853

Hi, 

I'm trying to understand a baptism record from Kilbeggan, County Westmeath.

James Mooney was baptised on 9 December 1853, but his parents seem to be James Carey and Mary Bastick. I don't understand why he should have a different surname. Looking at other baptisms, this seems to be quite a common feature. Am I reading the records incorrectly? Can anybody explain where I'm going wrong?  Thanks.