Nemertea
Nemerteans range in size from 5mm (0.2 in) to over 30 m (100 ft) long in the case of the European Lineus longissimus, with most species being 20 cm (8 in) or less. There are reports of specimens up to 50 or 60m  long, which would make it the longest animal in the world. The longest animal on record is a female blue whale, 29.9m long.