On some new Silurian [Ordovician] crinoids and shells

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ID: 294334
1871
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Abstract
COIUlllll very distinctly pentagonal, the angles at the cOllnection with the body being continuous with strong ridges passing up the sutures betwel'n the basal pieces allCl to the middle of the subradials.Bor1y pentagollal-obconic, a litde wider above than high.Base wider than high, strongly pentagonal, being deeply excavated up the middle of cach piec8, and vcry prominellt at the lateral sutures; basal pieces wider below than high, pentagonal in form, with the mesial angle above salielJt, and the superior lateral sloping sides much longer than the lateral.Sub radial pieces of moderate size, those seen, hexagollal in form, and all very convex in the middle, from which point they semI one strollgly elevated ridge to meet others 011 each of the surrounding plates, and others coming up the sutures between the basals, while on each side of all of these ridges, excepting sometimes those passing to the first radials above, there is Hsually a smaller, less elevated ridge; the snrtilCe of the body being thus divided by these ridges into very profoundly excavated triallglllar spaces, in the middle of which the corners of the body plates meet.First radial pieces, excepting one on the anal side, larger than the subrac1ials, abont as wide as high, with a general pentagonal outline, the upper side being longest and deeply excavated for the reception of the comparatively narrow free radials or arm pieces; one on the right of the :lnal serie~, shorter than the others, pentagonal in form, and supporting above another larger radial that is included a~ a part of the wall of thc body, and corrcsponds with the first radials in the other rays, excepting that it is shorter; all convex aud sending a strong ridge to each of the contiguous body plates below, while a number of much smaller ridges pass horizontally across from Olle to allother of these pieces Oil each side.Arms or free rays, comparatively ra(.her narrow, distinctly rounded on the outer or dorbal :,;ide, and composed of trallsversely oblong pieces that are about twice as wide as long below the first bifurcation; in the first rayon the right of the allal series, bifurcating on the fourth free piece, beyond which tbey are seen to be 10llg and composed of proportionally Ilarrow pieces; but their mode of bifurcation, if they (livide again, and their structure in the other rays, cannot be ma(le out from the specimens at ha11d.Anal series unknown.Ventral extension of the body more than four times as 1001g as the latter, and as seen flattened by pressure, of greater breadth; as usual, composed of numerous small equal hexagonal, alternately interlocking pieces, that are strengthened by little oblique costal so arranged as to present nn ascending zigzag appearance.Surface, excepting the strong costm of' the body plate:,;, and the smaller ones of the ventral part, without ornamentation.* Xow, since we know the nature of the v"ult of Cyathocrinites (see Proceed.
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openalex_W2313186240 Use this key to autocite in the manuscript while using SciMatic Manuscript Manager or Thesis Manager
Authors F. B. Meek
Journal american journal of science
Year 1871
DOI
10.2475/ajs.s3-2.10.295
URL
https://doi.org/10.2475/ajs.s3-2.10.295
Keywords Keywords not found

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