Complex sentence: There are 209 species of non-marine molluscs in the wild in Britain, and two of them ("Fruticicola fruticum " and"Cernuella neglecta") are locally extinct.
Split into simpler sentences: There are 209 species of non-marine molluscs that have been recorded as living in the wild in Britain. Two of them ("Fruticicola fruticum " and"Cernuella neglecta") are locally extinct.