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Published online by Cambridge University Press: 01 May 2009
Vicarious avicularia, that is to say avicularia substantially as large as zoœcia, have rarely been figured among the Cretaceous Cribrilinidse, the only good instances I call to mind being Escharipora incrassata, D'Orb., Membraniporella (Cribrilina) Falcoburgensis, Perg., the illustration of which shows a clear case, although no reference is made to it in the text, and Cribrilina ostreicola, Bryd. They are not, however, by any means so rare as this might suggest, and the four following species are probably not the only instances which will ultimately be added from the English Chalk.
page 1 note 1 Pal. Crét. Franc., v, p. 223, pl. 685, figs. 2, 3.
page 1 note 2 Bull. Soc. Belge Geol., 1893, p. 176Google Scholar et seq., text-fig. 7.
page 1 note 3 Geol. Mag., 1909, p. 399Google Scholar, Pl. XXIII, Figs. 1, 2.
page 2 note 1 Ante, p. 494.
page 2 note 2 Geol. Mag., 1909, p. 398Google Scholar.
page 3 note 1 Ibid., 1906, pp. 289–300, Fig. 7 (as Cribrilina Sherborni).
page 3 note 2 Ante, p. 146.
page 3 note 3 There is a very similar form in the Weybourne Chalk, in which according to my only good specimen the front wall has the slits usually obliterated by calcification, the aperture is very irregular in shape and sometimes sharply triangular owing to the encroachment of the accessory avicularia, the accessory avicularia are only slightly prominent, and the vicarious avicularia are longer and wider and expanded at the anterior end, being of the same general outline as those of Membranipora invigilata, Bryd. (Geol. Mag., 1910, p. 76Google Scholar), and the remains of the transverse bar are much more pronounced. I should not care to commit myself to its being a distinct species on practically one specimen, but if so it might be named M. Weybournensis.
