Family Hyalospheniidae Schultze, 1877 emend. Kosakyan and Lara 2012
Diagnosis: The test is rigid, colorless or yellowish-brown, flask-shaped, oval or pyriform, dorso-ventrally compressed. The shell is either entirely self secreted (e.g. Hyalosphenia) composed of an organic matrix, or with addition of self secreted siliceous plates (Quadrulella) or recycled shell plates of small euglyphids or other similar material such as diatom frustules incorporated in the test. The pseudostome is terminal and bordered by a thin collar.