. Catalogue of the Blastoidea in the Geological Department of the British Museum (Natural History) : with an account of the morphology and systematic positionof the group, and a revision of the genera and species. British Museum (Natural History). Dept. of Geology; Blastoidea. \ / / / i 0 Onus / i r af T A B Diagrams to show the relations of the dorsal and radial axes in Eleutherocrinus Cassedayi (adapted from Shumard aud Yandell). A, dorsal, and B, ventral aspect. A, B, C, D, E. The five radii of the calyx, basals. d . . d. The dorsal axis, situated. The small azygos basal, y, z. The two larg
. Catalogue of the Blastoidea in the Geological Department of the British Museum (Natural History) : with an account of the morphology and systematic positionof the group, and a revision of the genera and species. British Museum (Natural History). Dept. of Geology; Blastoidea. \ / / / i 0 Onus / i r af T A B Diagrams to show the relations of the dorsal and radial axes in Eleutherocrinus Cassedayi (adapted from Shumard aud Yandell). A, dorsal, and B, ventral aspect. A, B, C, D, E. The five radii of the calyx, basals. d . . d. The dorsal axis, situated. The small azygos basal, y, z. The two larger . . r. The radial axis, in which the anus is new species (E. Whitfield}), speaks of it somewhat infelicitously as the " Ventral basal ; Two of the radials, A and B, rest directly against the anterior edges of this azygos basal, while its rounded posterior border is in contact with two long and narrow plates, the paired basals, y and z, which extend nearly halfway up the side of the calyx (PI. XIX. fig. 5), and support a single spade-like radial closely resembling the radial plates of some species of Codaster (PI. XIII. fig. 3). The other four radials are deeply incised by narrow ambulacra of the usual character, but the two which are in contact with the azygos one are naturally slightly different from their fellows. Their ambulacra (C and E) are almost in a straight line (Fig. VIII.; PI. XIX. fig. 6), instead of forming an angle of twice 72° as in the regular Blastoids, and the azygos ambulacrum between them is altogether different from them. It is unusually wide, and entirely limited to the summit of the calyx. This is well seen in Mr. Wachsmuth's specimen (PI. XIX. fig. 6), which also shows the three normal deltoids, though we have not been able to make out the spiracles figured by Shumard 1 Fifteenth Ann. Rep. New York State Cab. Nat. Hist. 1S62, p. Please note that these images are extracted from scanned page images that may have been digitally enh
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