Revision of the Phyllocarida from the Chemung and Waverly Groups of Pennsylvania

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Abstract
It is now eighteen years since I prepared a memoir for the Second Geological Survey of Pennsylvania, describing the species of Phyllocarida then known from the Chemung (Upper Devonian) and Waverly (Lower Carboniferous) Groups in that State. Subsequent collecting at the original locality has yielded a quantity of material which further elucidates the characters of the original species, and also adds two distinctly new forms to the fauna of the Waverly Group. The specimens described in the present paper, as well as those on which the original descriptions were based, were all obtained in the vicinity of Warren (Pennsylvania). The chief horizon is in the shale-beds of the Upper Chemung Group, about 50 feet above mean water-level in the Alleghany River. At this level, crustacean remains are fairly abundant, and constitute a conspicuous element of the contained fauna. On this account, the deposits have been called by me ‘the Phyllocarid-Beds.’ The species thus far secured from the horizon are Echinocaris socialis, Tropidocaris bicarinata , and Elymocaris siliqua . Other forms are much less abundant, and occur in a sporadic manner in the higher strata. The following notes on the genera and species are to be considered, not as complete descriptions, but as additions and emendations to the original diagnoses. The new material representing this species, consisting of more than a hundred individuals, presents a greater range in size than was originally observed, and permits of a more exact description of the postabdomen, the ornamentation of the somites, and the number of lobes

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