Distribution, red, in Britain and Ireland.
There is an approximate correlation of the NBN records records.nbnatlas.org/occurrences/search?q=lsid:NBNSYS0000… of A. fascicularis with areas with a mean January temperature of 42°F (5.6°C) or above. This mean temperature, known to biogeographers as the ‘growing temperature’, is sufficient in non-exceptional years to maintain grass growth and avoid damaging frost on the seashore; it marks the approximate limit for several southern species.
The records east of the Isle of Wight may indicate a slightly greater tolerance of cold, misidentification or a shift east of the isotherm since 1929 when it was drawn.

KEY ID FEATURES : 01 Acanthochitona fascicularis