Abstract
THE Ophiuroidea have long presented a problem to the systematist, and its solution was not advanced when the palaeontologist joined the neontologist in council. The reason is twofold: the modern representatives of this Echinoderm class differ little in great points, but greatly in little points; the Palaeozoic representatives, which do differ much, and should throw light on the origins of orders, are so preserved as to be difficult of interpretation. Twenty-five years ago Mr. Jeffrey Bell divided the recent forms according as they could only move the arms horizontally or could also coil them vertically, the latter being regarded as more primitive. Dr. J. W. Gregory extended this system by adding an order for those yet more primitive forms in which the arm-bones still consisted of the original paired elements. It was, early pointed out that these divisions represented successive grades rather than divergent orders; but doubt has since been cast even on their correspondence with reality by the observations of Schondorf, Sollas, Mortensen, and Spencer on the older fossils and on the crucial genus Ophioteresis. Now a voice from the East complains: “I found the classifications very unsatisfactory. Indeed, their imperfections became a haunt to me.” From a study of recent genera, Mr. Matsu-moto infers that in respect to both mouth-frame and arm-bones the forms which can only move their arms horizontally are more primitive than those which can coil them vertically. He therefore rejects any system based mainly on the joint-faces, and puts forward a classification of his own.
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B., F. The Classification of the Brittle-Stars. Nature 100, 233 (1917). https://doi.org/10.1038/100233a0
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DOI: https://doi.org/10.1038/100233a0