Extract
In 1825 J. de C. Sowerby described and figured as Spirifer lineatus a brachiopod from the “ Wenlock Limestone ” of Dudley, choosing three syntypes; later he changed the specific name to radiatus. Of subsequent descriptions those of Hall (1852), Davidson (1866), Beecher and Clarke (1889), and Hall and Clarke (1894) are the most important. The present study is based on topotype material, while additional specimens for comparison have been collected by the writer from the Wenlock Shale of Malvern (Colwall Tunnel Tip Heap), from the Woolhope Limestone of Suckley, from the Wenlock Limestone of May Hill, and from the Tickwood beds and Wenlock Limestone on Wenlock Edge (railway cuttings near Presthope and Lilleshall Quarry). These, together with specimens from the Sedgwick Museum Collection, from the Birmingham University Collection, and from the British Museum (Natural History), have provided material adequately representative of variations in shape and size. Study has been made of external features, but more particularly of internal characters. The method of investigating the internal structures consists in grinding down the specimen either from the umbones, or from the lateral margin, and taking serial cellulose transfers at regular intervals, from which enlarged scale models may be constructed. Five specimens have been so treated, and as well as the construction of models, use has been made of perspective scale drawings to show the variations in internal structure. Growth lines are preserved on the transfers, but have in addition been examined in thin sections; specimens from Haverfordwest and Rubery preserved as casts have served to throw light on the muscle system, while finally the ventral valves of specimens preserved in shale, have been prepared to show the variations in internal structure.