The skeleton of sponges consists of microscopic calcareous or silicious spicules. The poriferan 'skeleton' consists of microscopic calcareous or siliceous spicules or a spongin network. The suborder Scleraxonia species are supported by a skeleton of tightly grouped calcareous spicules. These aggregates of bony matrix are called bone spicules. This allows them to form their large siliceous spicules exclusively inside their cells. During the formation of bone spicules, cytoplasmic processes from osteoblasts interconnect. This may be calcified, forming structures such as shells, bones, and spicules. The weaker spicules of trabecular bone break ("microcracks"), and are replaced by weaker bone. Each of the spicules is a single crystal of mineral calcite. Males possess small spicules and small bursae or alae. The girdle is often ornamented with spicules, bristles, hairy tufts, spikes, or snake-like scales. The skeletons are made up of either ten diametric or twenty radial spicules. Unroofing the early vesicles or pustules may permit manual extraction of the spicules. Siliceous oozes often contain lesser proportions of either sponge spicules, silicoflagellates or both. The larvae form a sophisticated endoskeleton that is made of two spicules.