Gardai in Howth are investigating the discovery of a human skull on Burrow beach Sutton.
It was discovered by a man while out walking at lunchtime.
Gardai attended the scene and were assisted in searching the area by Dublin Coast Guard.
A small bone, also believed to be human, was located in the follow-up search.
The skull was examined by a doctor and confirmed to be human. It was taken to the city morgue for further examination.
A garda spokesman said the skull appeared to have been in the sea for a long period of time.
Investigations are ongoing to establish the identity of the person and a cause of death. At this point it is suspected that the bones may belong to one of many people who went missing at or near the sea either in Ireland or along the coast in the UK.
In October 2012 a similar investigation was launched after a human arm was found washed up on a south Dublin beach.
The grim discovery was made by gardai on patrol at Shankill Beach.
The right arm was taken to the city morgue for forensic examination.
In February 2011 a human arm was found on a beach in Donabate and later identified as belonging to convicted rapist James Nolan (46), from Finglas, who had not been seen since his release from Portlaoise jail the previous November.