FIG. 18 in A revision of the supraspecific classification of the subclass Calcaronea (Porifera, class Calcarea)

FIG. 18. — Diagram of a transverse section through the wall of Grantia socialis Borojevic, 1967. Abbreviations: a, atrium; as, atrial skeleton composed of tangential triactines and tetractines; ss, subatrial spicules; ar, articulate choanosomal skeleton; cx, cortex (from Borojevic 1967a). Scale bar: 100 µm.