A. "Clathrina rubra" (Calcinea, Clathrinida), NW Mediterranean Sea (photo courtesy Jean Vacelet); B. Calcinean spicules: equiangular and equiradiate triactines (photo courtesy Jean Vacelet); C. "Guancha lacunosa" (Calcinea, Clathrinida), NW Mediterranean Sea; D. "Petrobiona massiliana" (Calcaronea, Lithonida), two specimens from caves, NW Mediterranean Sea. Spicule complement of "P. massiliana": from left to right pugiole, sagittal triactines, microdiactine (photos courtesy Jean Vacelet); E. Calcaronean spicules: sagittal (inequiangular) triactines and diactines; F. Syconoid aquiferous system from "Sycon ciliatum" (SEM photo, courtesy Louis De Vos, ULB); G. "Sycon ciliatum" (Calcaronea, Leucosolenida), specimen about 10 cm, from the English Channel.