Cylindrical forms with a conical prostomium and four jaws. The mouth is on the ventral surface and is overhung by the prostomium (proboscis). The peristomium is a ring, often hidden dorsally by the prostomium and the first segment. It houses a brain and may be homologous to the prostomium of other annelids. The head is formed by the fusion of a funnel-shaped, symmetrical peristomium with the prostomium. This region is described as medial, and corresponds to the annelid prostomium. The head consists of two segments&colon; the anterior and posterior prostomium. Tentacles extended from the prostomium and may have served as sensory organs. The prostomium has no appendages or palps. Its palps are papilliform and with palpophores, inserted laterally on its prostomium. The head has no appendages, palps or eyes but has a prostomium and evertable oesophagus. Its prostomium has digitiform paired antennae inserted dorsally. The shape and composition of prostomium are important for annelid systematics. The prostomium, the front-most segment, is slightly lobed and bears two eyes and five antennae. The body is cylindrical and the prostomium bears three antennae and four eyes.