Cuilcagh () is a mountain on the border between County Fermanagh (in Northern Ireland) and County Cavan (in the Republic of Ireland). With a height of it is the highest point in both counties. It is also the 170th highest peak on the island of Ireland, and Ireland's only cross-border county top. Water from the southern slope flows underground until it emerges some miles away in the Shannon Pot, the traditional source of the River Shannon. The area is sometimes referred to as the Cuilcagh Mountains. Naming The name Cuilcagh comes from the Irish Cuilceach, which has been translated as "chalky". However, the mountain is mainly sandstone and shale, covered with bog and heather. The cliff-edged summit surface of the mountain is formed from the hard-wearing Lackagh Sandstone which itself overlies the Briscloonagh Sandstone. "It is possible that the name refers to the limestone rock on the lower northern flanks, namely the Glencar and Dartry Limestone formations. Here a number of streams disappear below ground at swallow holes named Cats Hole, Pollawaddy, Pollasumera and Polliniska, all forming part of the Marble Arch cave system. If so, the name would mean 'calcareous' rather than 'chalky'". It has also been called Slieve Cuilcagh in English, 'Slieve' being an anglicisation of Sliabh ("mountain"). In the 1609 Plantation of Ulster, Cuilcagh formed part of lands which were granted to John Sandford of Castle Doe by letters patent dated 7 July 1613 (Pat. 11 James I – LXXI – 38, Quilkagh). It was later sold by Sandford to his wife's uncle Toby Caulfeild, 1st Baron Caulfeild, Master of the Ordnance and Caulfield had the sale confirmed by letters patent of 12 July 1620 (Pat. 19 James I. XI. 45, Quilkagh). Nature The Cuilcagh area supports a rich assemblage of upland insects, and is one of the most important sites in Ireland for these species. Species recorded include the water beetles Agabus melanarius, Agabus arcticus, Dytiscus lapponicus, Stictotarsus multilineatus, Hydroporus longicornis and Hydroporus morio and the water bugs Glaenocorisa propinqua and Callicorixa wollastoni. Lough Atona is the main locality for these species. Conservation The Cuilcagh Mountain Park was opened by Fermanagh District Council in 1998. Ramsar site The Cuilcagh Mountain Ramsar site (wetlands of international importance designated under the Ramsar Convention), is 2744.45 hectares in area, at latitude 54 13 26 N and longitude 07 48 17 W. It was designated a Ramsar site on 31