Petalocrinus , Weller & Davidson

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Abstract
Among the geological collections from Gotland, preserved in the Riksmuseum at Stockholm, there have long been some curious fan-like objects, obviously echinodermal, but beyond that of doubtful significance. Study of these in September 1890 led to the conclusion that they were crinoidal; not cup-plates, however, as some had supposed, but dichotomous arms in each of which the branches were fused together, forming what may be termed an ‘arm-fan.’ Although it seemed probable that they were of Inadunate affinities, they were not, in the absence of more precise evidence, described in Part I of ‘The Crinoidea of Gotland’ (Kongl. Sv. Vet.-Akad. Handl. vol. xxv, No. 2, Dec. 1893). Fortunately, about this time Mrs. A. D. Davidson, now of Whiting (Ind.), discovered in the contemporaneous rocks of Iowa similar fossils, two of which retained the five arm-fans in their natural position, like the petals of a dog-rose around a small calyx (text - fig. 1). These were shown to me by Mrs. Davidson on her visit to England in the summer of 1891, and proved the correctness of my surmise concerning the Gotland fossils. The Iowa specimens, however, were taken back to America, and subsequently submitted by their owner to the Assistant in Palæontologic Geology at the University of Chicago, Mr. Stuart Weller, who prepared a paper entitled ‘ Petalocrinus mirabilis (n. sp.) and a New American Fauna.’ Now that Mrs. Davidson's more complete individuals have been described, and the genus erected on their broader basis, it is time to describe the three

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