Type species: Tharyx monilaris Hartman, 1960. Designated by Blake 1991.
Diagnosis (emended). Prostomium conical to rounded; peristomium elongate to as long as wide, with pair of grooved dorsal tentacles arising either on or anterior to setiger 1; thoracic region often expanded, thoracic segments crowded or uncrowded; abdominal segments sometimes beaded in appearance; setae simple capillaries lacking distinct serrations using light microscopy but distinct fibril endings may be visible using SEM; posterior end frequently expanded, tapering to a simple pygidial lobe.
Remarks. The generic diagnosis was modified slightly to include the rounded prostomium of A. zebra sp. nov. Based upon setal morphology revealed using SEM it was necessary to stress that the lack of distinct serrations in this genus refers to their appearance using light microscopy. These serrations seen in SEM for some species of Aphelochaeta are visible fibril endings irregularly protruding along the shaft of the seta, typically with pointed tips and often frayed. These are structurally different from the protruding denticles or teeth found on setae in members of the genus Monticellina.