XVI.—Note on an Algal Limestone from Angola

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Abstract
The specimens here described were collected by Professor J. W. Gregory in Angola, and belong to the series described in the paper by him on the geology of that country.The horizon of the beds from which the limestone was obtained is Albian.The specimens are of a yellowish pisolitic limestone. In hand specimens the weathered surface has a warty appearance—the diameter of each knob being about 1 cm. A fractured surface shows circular forms varying in size and having decided concentric markings. These concentric markings are, however, less evident in microscopic sections, and this is probably due to the effects of preservation. A similar case has been described by Mr H. Yabe, where the genus Metasolenopora is affected in this way. These circular forms make up the greater part of the rock, and are cemented together by a fine calcareous paste in which are fragments of shell and quartz grains, with occasional grains of other minerals, such as felspar and muscovite. The specimens of limestone examined varied to some extent in texture, some being more compact, and even slightly siliceous, but the contained organisms are present in similar amounts regardless of the texture of the rock.

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