Cordon

In Nematodes,Longitudinal, cuticular cord-like thickening extending posteriorly from the mouth and may be straight,recurved or form loops,present mainly in the Spiruroid family Acuaridae(Anderson 1974),their Shape and Size is important in Taxonomy.They can be :

Anastomosing e.g. Desportesius spp 

Not-anastomosing , Recurrent ,Non-recurrent

Or even for a Collarette e.g.  Stegophorus