 Nemertea is a phylum of invertebrate animals also known as " ribbon worms " or " proboscis worms " . Alternative names for the phylum have included Nemertini , Nemertinea and Rhynchocoela . Although most are less than 20 centimetres ( 7 @.@ 9 in ) long , one specimen has been estimated at 54 metres ( 177 ft ) . Most are very thin , with a few exceptions such as the giant ribbon worm .
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The name Nemertea is derived from the Greek word nemerte , meaning " ribbon " .
The phylum consists of a few hundred species in 24