Complex sentence: It is also used to refer to the rock strata those deposits are found in, both in Britain and in the Rhenish hill countries (the Culm Measures), and to coal exported from Britain during the 19th century.
Split into simpler sentences: It is also used to refer to the rock strata whose deposits are found in both Britain and in the Rhenish hill countries (the Culm Measures). It may also refer to coal exported from Britain during the 19th century.