Colpomenia peregrina (Sauvageau) Hamel is a seaweed (alga) not native to the British Isles but recorded in Ireland since 1934. Seaweed is a loose colloquial term encompassing macroscopic Multicellular, benthic marine Algae. Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms The British Isles (Irish variously Na hOileáin Bhriotanacha, Oileáin Iarthair Eorpa, Éire agus an Bhreatain Mhór; Ellanyn Goaldagh Eileanan Ireland (pronounced /ˈaɾlənd/ Éire) is the third largest island in Europe, and the twentieth-largest island in the world It appears to have been introduced from the Pacific and was first noticed in Europe in 1906 on oyster beds. The Pacific Ocean is the largest of the Earth 's Oceanic divisions The common name oyster is used for a number of different groups of Bivalve Mollusks most of which live in marine habitats or Brackish water. It has now been recorded throughout the eastern north Atlantic from Norway and Sweden to Portugal. Norway ( Norwegian: Norge ( Bokmål) or Noreg ( Nynorsk) officially the Kingdom of Norway, is a Constitutional "Sverige" redirects here For other uses see Sweden (disambiguation and Sverige (disambiguation. Portugal, officially the Portuguese Republic (República Portuguesa is a country on the Iberian Peninsula.  It was first recorded Britain in 1908 and in Ireland in 1934. 
Colpomenia is a brown alga in the Phylum, or Division, (Heterokontophyta), the Class Phaeophyceae and the Order Sphacelariales. 
Colpomenia peregrina (syn. Colpomenia sinuosa (Mertens ex Roth) Derbès et Solier var. peregrina Sauvageau) is a small brown alga, bladder-like, hollow and membranous, up to 9 cms across. The surface is thin and smooth but often collapsed or torn when older. Olive brown in colour and attached by rhizoidal filaments to rock at the base.  There are two species in Europe: C. sinuosa (Mert. ) Derb. & Sol. and C. peregrina (Sauvageau) Hamel. C. sinuosa was present at least as far back as the 1840s in Spain and C. Spain () or the Kingdom of Spain (Reino de España is a country located mostly in southwestern Europe on the Iberian Peninsula. peregrina was introduced and first noticed by oyster fishermen in the Bay of Biscay in 1906. Cantabrian Sea redirects here Not to be confused with Biscay Bay Newfoundland and Labrador or Biscayne Bay. It was first noticed in Britain in 1907 in Cornwall and Dorset. Cornwall ( Kernow ˈkɛɹnɔʊ is the most southwesterly county of England, on the Peninsula that lies to the west of the River Tamar Dorset ( (or archaically, Dorsetshire) is a county in South West England on the English Channel coast  The two species are superficially similar and in older texts, such as Knight and Parke (1931), C. peregrina is referred to as C. sinuosa.
Leathesia difformis (L. ) Aresch. is similar, it is yellow brown in colour, fleshy and mucilaginous in texture. It is globose and smooth when young becoming hollow and convoluted with age and growing to 5 cms in diameter.  It is easily distinguished as it readily squashes when pressed under finger and thumb. 
Found in littoral rock pools, not exposed and in the sublittoral to 3m depth. 
There are specimens stored in the Ulster Museum Herbarium (BEL) from counties in Northern Ireland, Co. The Ulster Museum is located in the Botanical Gardens in Belfast, Northern Ireland, and has around 8000 square metres of public display space featuring Donegal and Wales under the catalogue numbers: F11254; F3136; F7675; F6154; F1682; F1693; F7491; F7674; F4254; F4254 and F1832.
Ireland: Colpomenia peregrina has been recorded in Ireland from Counties: Down, Donegal, Kerry, Galway, Clare and Cork. Ireland (pronounced /ˈaɾlənd/ Éire) is the third largest island in Europe, and the twentieth-largest island in the world Ireland (pronounced /ˈaɾlənd/ Éire) is the third largest island in Europe, and the twentieth-largest island in the world County Down, ( Ulster Scots: Coontie Doun. is one of the nine counties that form the province of Ulster and one of six counties that form Donegal ( Irish: Dún na nGall) is a town in County Donegal, in the Province of Ulster, in Ireland. County Kerry ( Contae Chiarraí in Irish) is a southwestern county of Ireland. County Galway (Contae na Gaillimhe is located on the West Coast of Ireland. County Clare ( Irish: Contae an Chláir) commonly referred to as simply Clare, is a county on Ireland and part of the wider County Cork (Contae Chorcaí is the most southerly and the largest of the modern counties of Ireland.  Apparently this alga was first recorded in Ireland by M. J. Lynn from Strangford Lough in March 1934 and from Lough Larne near Ballycarry and Magheramorne in 1935. Strangford Lough ( describing the fast-flowing Narrows; and Loch Cuan in Irish meaning the calm Lough describing the gentle Waters Larne (&mdashthe domain of a Viking chieftain is a substantial seaport and industrial Town on the east coast of County Antrim, Northern Ireland It was also recorded from Portballintrae, on the north coast, and in the south at Lough Ine. In 1936 it was found at Rush (County Dublin) and at Killough (County Down). County Dublin (Contae Bhaile Átha Cliath or more correctly today the Dublin Region ( Réigiúin Átha Cliath) is the area that contains the city of Dublin There are further records of from: Portstewart (County Londonderry), cast ashore at Hood's Ferry, Islandmagee (opposite Larne), (County Antrim). County Antrim ( Contae Aontroma or simply Aontroim in Irish) is one of six counties that form Northern Ireland, and one of nine counties  It is now abundant.
Britain: Generally around the British Isles.  In Hardy and Guiry (2006) it is shown to be generally recorded around Ireland, south west England, Wales and the west coast of Scotland. England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland Scotland ( Gaelic: Alba) is a Country in northwest Europethat occupies the northern third of the island of Great Britain. Records from the east of Scotland are few and it not shown as present on the east or south east coast of England.  It is noted as a recent addition to the flora (as C. sinuosa in Knight and Parke (1931). 
America (west): Alaska to La Jolla, California.