There are several constants of value in the determination of this species. They are:—(1) The epithecal characters; (2) the spacing of the major septa (i.e. their number in a given diameter); (3) the thickening of stereoplasma in the lower and conical part; (4) the characters of the dumonti phase (PI. VI, Figs, 1b–1d and 2a–2d); (5) the nature of the dissepiments, and their restriction to the mature growth stages; (6) the nature of the tabulæ. Of these, (2), (4), and (6) are of particular importance.