Euphausiacea: Adults

There  are only 6  species of euphausiids that reside permanently and breed in  the  North Atlantic, north of 40" N. These are: Thysanopoda acutifrons HOLT & TATTERSALL, Nyctiphanes couchii (BELL), Meganyctiphanes  norvegua (M. SARS), Thysanoessa inermis ( KRØYER), T. longicaudata (KRØYER) and T. raschii (M. SARS). A further 8 species occur fairly commonly in southern regions of the  North Atlantic and are occasionally caught in more northern  areas; these are Bentheuphausia amblyops G. O. SARS, lhysanopoda microphthalma G. 0. SARS, Euphausia krohnii (BRANDT), Thysanozssa gregaria G. O. SARS, Nematoscelis megalops G. O. SARS, Nematobrachion boopis (CALMAN), Stylocheiron  elongatum G. O. SARS, S. longicorne G. O. SARS, S. maximum HANSEN, and S. abbreviatum G. O. SARS. These species are all included in the key presented here. 

Occasional individuals of other species have been recorded in the sea area lying between southern Ireland and 40' N (see MAUCHLINE & FISHER, 1969) but these species have not been included in the key. If a species is  not identified by the key given here then recourse should be made to the fuller key and to  the sources of original descriptions of species given in MAUCHLINE & FISHER (1969).