身体细长、比较神秘的陆地无脊椎动物，生长在潮湿阴暗的温带地区，与环虫动物门截然不同，与蛞蝓的腿相似，有时被认为介于环节动物和节肢动物之间

• enigmatic small elongated wormlike terrestrial invertebrates of damp dark habitats in warm regions; distinct from the phylum Annelida; resemble slugs with legs and are sometimes described as the missing link between arthropods and annelids