. The Devonian crinoids of the State of New York. Crinoidea, Fossil; Paleontology; Paleontology. DEVONIAN CRINOIDS OF NEW YORK 337 undivided arm (borne by the left anterior superradial) lies above the other arms and serves as a protection to the crown, particularly against tidal currents. Jaekel's explanation of the habit of these forms is, I think, more natural. Certainly the animal with crown erect is in a better position, as pointed out by Jaekel, for the food to be carried to the mouth along the ambulacral furrows than if the arms were pendent. According to Jaekel's views the specimens of
. The Devonian crinoids of the State of New York. Crinoidea, Fossil; Paleontology; Paleontology. DEVONIAN CRINOIDS OF NEW YORK 337 undivided arm (borne by the left anterior superradial) lies above the other arms and serves as a protection to the crown, particularly against tidal currents. Jaekel's explanation of the habit of these forms is, I think, more natural. Certainly the animal with crown erect is in a better position, as pointed out by Jaekel, for the food to be carried to the mouth along the ambulacral furrows than if the arms were pendent. According to Jaekel's views the specimens of this group, as figured on plate 41, are in an incorrect position. Genus HALYSIOCRINUS Ulrich 1886 (em. Bather 1893) Halysiocrinus secundus (Hall) n. comb. Plate 41, figures 6-9; text figures 55-5 7 1872 Calceocrinus (Cheirocrinus) secundus Hall. N. Y. State Mus. Bui. 1, pi. 1, figs. 13, 14- (Photographic plates distributed privately.) "-P Dorsal cup. A comparatively small, slender species. Dorsal cup, seen from the left anterior radius, narrow at the base; becomes somewhat constricted medially, and Figure 55 Diagram of widens out again rather abruptly at the arm bases. One specimen gives the following measurements: width at base, mm; width at median constriction, 5 mm; width at arm bases, mm. Basals fused to three, forming a fairly large, sub- triangular, convex plate, which measures mm along its articulating edge. Left posterior and left anterior basals fused, forming what is styled an anterior basal. Anterior basal triangular; its length, measured along the hinge line, mm. It will thus be seen that mm of the length of the hinge line is made up by the pos- terior and right anterior basals. Stem attached along the suture line of the right anterior and posterior basals, and about .5 mm from the point of union of the three basal the posterior side of Halysiocrinus. (After Bather, 1893). /. B, the " anterior basal " formed by the fusion
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectpaleont, bookyear1923
