Revision of the genus Clathrina (Porifera, Calcarea) Author Klautau, Michelle Author Valentine, Clare text Zoological Journal of the Linnean Society 2003 2003-09-30 139 1 1 62 https://academic.oup.com/zoolinnean/article-lookup/doi/10.1046/j.0024-4082.2003.00063.x journal article 10.1046/j.0024-4082.2003.00063.x 0024-4082 5432634 SUBCLASS CALCINEA BIDDER, 1898 Diagnosis: Calcarea with regular (equiangular and equiradiate) or exceptionally parasagittal or sagittal triactines and a basal system of tetractines. In terms of ontogeny, triactines are the first spicules to be secreted. Choanocytes are basinucleate with spherical nuclei. The basal body of the flagellum is not adjacent to the nucleus. Calcinea incubate coeloblastula larvae.