. The Crinoidea flexibilia (with an atlas of and 76 plates). Crinoidea, Fossil. LECAXOCRINIDAE 201 NIPTEROCRINUS Wachsmuth Plate XV Nipterocrinus Wachsmuth in Meek and Worthen, Proc. Acad. Nat. Sci., Philadelphia, Dec, 1868, p. 341.—Meek and Worthen, Geol. Surv., Illinois, V, 1873, p. 434.—Von Zittel, Handbuch Palaeon- tologie, I, 1879, P- 352-—Wachsmuth and Springer, Revision Palaeocrinoidea, pt. 1, 1879, p. 55; ibid., pt. 3, 1886, pp. 145, 188.—Miller, N. A., Geology and Palaeontology, 1889, p. 262.—Bather, Treatise on Zoology (Lankester), pt. 3, 1900, p. 188.—Springer, Amer. Geologis
. The Crinoidea flexibilia (with an atlas of and 76 plates). Crinoidea, Fossil. LECAXOCRINIDAE 201 NIPTEROCRINUS Wachsmuth Plate XV Nipterocrinus Wachsmuth in Meek and Worthen, Proc. Acad. Nat. Sci., Philadelphia, Dec, 1868, p. 341.—Meek and Worthen, Geol. Surv., Illinois, V, 1873, p. 434.—Von Zittel, Handbuch Palaeon- tologie, I, 1879, P- 352-—Wachsmuth and Springer, Revision Palaeocrinoidea, pt. 1, 1879, p. 55; ibid., pt. 3, 1886, pp. 145, 188.—Miller, N. A., Geology and Palaeontology, 1889, p. 262.—Bather, Treatise on Zoology (Lankester), pt. 3, 1900, p. 188.—Springer, Amer. Geologist, XXX, 1902, P- 95» Jour. Geology, XIV, 1906, p. 519.—Zittel-Eastman, Textbook Paleontology, 2d Ed., 1913, p. <y ^fy- & Fig. 21. Nipterocrinus Lecanocrinidae with rays above radials separated by perisome only. Crown elongate; calyx well differentiated. Infrabasals large, forming part of calyx wall, apparently fused into a discoidal plate. No radianal or anal plates. Interbrachial areas wide, occupied by perisome passing into the tegmen. Primi- brachs three (or four). Radial facets not filling distal face of radials. Arms dichotomous, divergent. Column large, long, cylindrical, not (or but slightly) enlarging at the calyx; with radicular cirri or branches at distal end. Genotype. Nipterocrinus wachsmuthi Meek and Worthen. Distribution. Lower Carboniferous, Burlington limestone; United States. This genus may be called the Carboniferous successor of Pycnosaccus, having a well- differentiated calyx with both radianal and anal plates eliminated. The general habitus— with large radials and narrow brachials, without regular interbrachials but the spaces filled by perisome—is identical with that of the Silurian genus, and the superficial resemblance is also very striking, especially to forms like Pycnosaccus zvelleri (PI. XIII, figs. 3-5). The three or more primibrachs, which in that species are exceptional for the genus, are the rule in Nipterocrinus.
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