Testate amoebae with proteinaceous shells: (A, B) Hyalosphenia papilio – shell composed of mucoprotein; (C, D) Arcella gibbosa – shell composed of numerous hollow building units (alveoli).

 
 
  Part of: Todorov M, Bankov N (2019) An Atlas of Sphagnum-Dwelling Testate Amoebae in Bulgaria. Advanced Books. https://doi.org/10.3897/ab.e38685