Edrioaster bigsbyi was first made known by E. Billings in June, 1854, and was referred by him, though with some doubt, to Agelacrinites. He gave no specific name, but regarded his fossils as identical with the specimen found by Bigsby at the Chaudière Falls and described by G. B. Sowerby in 1825 (see Study III), and as “almost identical with A. Buchianus” of Forbes, 1848 (see Study II). This series of papers by Billings contains several important observations and reasonings not reproduced in those later more official publications of his to which alone subsequent writers seem to have gone for information. From the original account it is clear that the specimens there called Agelacrinites were the same as those which Billings described in 1857, under the name Cyclaster bigsbyi. The misapprehension that caused Billings to apply to his new species the trivial name bigsbyi has already been dealt with in Study III; the species has nothing to do with the specimen found by Bigsby. In 1858 Billings discovered and pointed out his error, and, realizing further that the generic name Cyclaster had been taken by G. Cotteau for a sea-urchin a few months before his own use of it, he redescribed the species under the name Edrioaster bigsbyi. The independence of the genus itself was denied in 1860 by E. J. Chapman, who referred the species back to Agelacrinites. The textbook writers, however, generally accepted Edrioaster, and no change was made in either name or description until Professor Haeckel in 1896 thought fit to alter the name to Edriocystis.