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Published online by Cambridge University Press: 01 May 2009
A developmental sequence of Membraniporellæ showing progressive subordination of the ribbed front wall to a solid secondary front wall can be traced fairly directly from Membraniporella pustulosa, Bryd., which is prevalent in the zone of M. cor-anguinum and the Uintaerinus band and seems to die out in the zone of Marsupites. In the zone (restricted) of A. quadratus it is succeeded by
Membraniporella thoraciformis, sp. nov. (PL IX, Figs. 1–3.)
Zoarium unilaminate, incrusting.
page 145 note 1 Geol. Mag., 1910, p. 483, Pl. XXXVI, Fig. 9.Google Scholar
page 147 note 1 Geol. Mag., 1909, p. 398, Pl. XXII, Figs. 4, 5.Google Scholar