Description

 The horseshoe worm Phoronis muelleri is elongated and worm- shaped. The mouth is surrounded by a characteristic horseshoe shaped arangement of tentacles known as the lophophore. Phoronis muelleri can be up to 12 cm in length but less than 1 mm in width. The body is a pinkish colour and the lophophore is transparent, sometimes with spots. The lophophore of Phoronis muelleri sometimes has medially turned ends and the numerous tentacles are notably shorter near the mouth but may reach up to 2 mm in length.Phoronida have a characteristic ciliated and free-swimming pelagic larva, known as Actinotrocha. Separate names for larval and adult forms may still be used in taxonomy (Emig, 1979).