Baerida
Baerida is an order of sea sponges in the subclass of Calcaronea.
Species of the order Baerida are leuconoid calcareous sponges with the skeleton either composed exclusively of microdiactines, or in which microdiactines constitute exclusively or predominantly a specific sector of the skeleton, such as choanoskeleton or atrial skeleton. Large or giant spicules are frequently present in the cortical skeleton, from which they can partially or fully invade the choanoderm. In sponges with a reinforced cortex, the inhalant pores can be restricted to a sieve-like ostia-bearing region. Dagger-shaped small tetractines are frequently the sole skeleton of the exhalant aquiferous system. Although the skeleton may be highly reinforced by the presence of dense layers of microdiactines in a specific region, an aspicular calcareous skeleton is not
