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Sphenopteris, or "wedge-fern," is the name applied to another coal-fern; glossopteris, or "tongue-leaf"; cyclopteris, or "round-leaf"; odonlopteris, or "tooth-leaf," and many others, show their chief characteristics in the names which they individually bear. Alethopteris appears to have been the common brake of the coal-period, and in some respects resembles pecopteris. Sphenopteris Affinis.
Though no regular seams of coal were formed, the characteristic imbedded coal-plants are of the genera Cyclopteris and Alethopteris, agreeing with species occurring at much higher levels, and distinct from those of the antecedent Devonian group.
Walchia piniformis, Schloth. Permian, Saxony. Branch. b. Twig of the same. c. About 18 or 20 species of plants are known in the Permian rocks of England. None of them pass down into the Carboniferous series, but several genera, such as Alethopteris, Neuropteris, Walchia, and Ullmania, are common to the two groups.
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