That detail, mundane and oddly specific, is one of the stranger things to emerge from the ground at Holmpatrick in north County Dublin, where a Late Bronze Age enclosure has been quietly confirmed beneath what was otherwise unremarkable terrain. The shells form the basal, or lowest, fill of the ditch, suggesting that whatever activity took place here, the sea and its harvest were part of it.

The enclosure was identified through a geophysical survey carried out by Earthsound (Licence Ref.: 16R0095) and subsequently confirmed through test-excavation, which also revealed a total of twelve separate Archaeological Areas in the vicinity. The enclosure itself is oval in plan, measuring approximately 53 metres on its north-south axis, and was defined by a ditch between two and two and a half metres wide, cut in a V-shape to a depth of between 1.25 and 1.85 metres. A V-shaped ditch profile is a common feature of prehistoric enclosures, efficient to dig and effective at defining a boundary. The ditch contained three distinct fills, with those shell deposits at the base. Above them, excavators recovered Late Bronze Age coarse ware pottery sherds and a hammer stone, objects that speak to domestic or small-scale industrial activity rather than anything ceremonial. The geophysical survey also identified an entrance in the eastern portion of the enclosure, and features within the interior include a pit, a posthole, and a series of linear and irregular features. The work was reported by Bailey and McIlreavy in 2016.

Holmpatrick is a townland in the Skerries area, and the enclosure lies within a landscape that has seen considerable development pressure over the years, which is precisely why survey and excavation work of this kind tends to happen here. There is nothing to see at ground level now; the enclosure survives as a subsurface feature rather than a visible earthwork. For anyone interested in the archaeology of the area, the published report by Bailey and McIlreavy is the most direct route into the detail of what was found, and the site itself serves as a useful reminder that the coastal margins of north Dublin were occupied and worked long before any written record begins.