carchesium carchesium carchesium is a genus of usually colonial peritrich ciliates in the vorticellidae with a spirally contractile stalk. the inverted bell-shaped cells have an oral lip as in epistylis carchesium scientific classification (unranked): sar phylum: ciliophora class: oligohymenophorea subclass: peritrichia order: sessilida family: vorticellidae genus: carchesiumehrenberg, 1830 the genus has a cosmopolitan diribution in freshwater and is a common part of the fauna of the aerobic stages of waste water treatment plants, such as activated sludge and trickling filters.