Memoirs of the Geological Survey of the United Kingdom —— Figures and Descriptions Illustrative of British Organic Remains

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ISBN: 9781333085223 出版年：2016 页码：27 Geological Survey of Great Britain Forgotten Books

It would appear from these facts that the ventral edge of the aperture of the phragmocone is parallel to the sutures of the septa, and that, on the sides, it curves round almost at a right angle to form an elongated lobe, which terminates in an ogive arch on the dorsal side.