Monaxon (diactinal) spicule pointed at both ends (a-m in figure). Different types are distinguished by shape and tip morphology. Shape may be fusiform (a), angulate (b), centrotylote (c), curved (d), or flexuous (e). Tips may be acerate (f), asymmetrical (g), blunt (h), conical (i), hastate (j), mucronate (k), stepped (1), or symmetrical (m).
Spicules of Demospongiae