Proceedings of the Washington Academy of Sciences Volume 2 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1900 Excerpt: ...delicate, and only partially attached; spreading out in a fan-shaped expansion, the gelatinous margin of which is often convoluted; the apposed surfaces often growing together and forming irregular ridges over the colony. Zcecia oblong, quadrangular in the younger stages, much narrowed below in the older, and disposed in alternate series. In the adult stage, the upper half of the zcecia 1 front is occupied by a membranous area, containing the crescent-shaped orifice at its distal end. The lower half is traversed by a network of calcareous lines or ribs which extend from the lateral margins and converge, either to a central line extending from the base of the zcecia or to the base of a raised portion of the zcecial wall just below the aperture. An avicularium is developed upon this raised portion, with mandible directed to one side. CEcia? This species seems to afford a transition between the Flustridae and the Membraniporidae. It possesses flustrine characteristics in the shape of the zcecium in the younger stages, and in the free frond-like growth of part of the colony. Where it is attached, however, the mode of adherence is membraniporidan. The thickened rim of the zcecium grows fast to the substratum, and upon removal of the crust the oblong shape of the under surface is left in outline. The type of avicularia is that of Membranipora, as is also the secondary calcification of a portion of the front wall. In a colony of moderate size, three stages of growth can easily be distinguished. Upon the growing edge the zcecia are but faintly outlined, and the aperture occupies the whole of the front (fig. 9a, ap.). This shape is retained through the next four or five rows, but the second stage begins in the calcification of the lower half of the zcecia and the st...