Kentucky Fossil Shells; A Monograph of the Fossil Shells of the Silurian and Devonian Rocks of Kentucky

Kentucky Fossil Shells; A Monograph of the Fossil Shells of the Silurian and Devonian Rocks of Kentucky

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1889 edition. Excerpt: ...rare, though it is very difficult to procure good specimens. Spirifera duodenaria. Hall. Plate XII., figures 12, 13 and 10. Delthyris duodenaria, Hall. Geol. Rep. 4th Dist. N. Y., p. 171, figure 5--1843. Spirifer duodenaria. Hall. Catalogue in Rep. on State Cabinet. Spirifera duodenaria, Hall. Pal. N. Y., Vol. IV., p. 189, pi. 27 and 28. Shell transverse, semi-circular; hinge-line equal to greatest width of shell; cardinal extremities obtuse or acute, rarely acuminate; valves sub-equally convex; area very narrow. Surface plicated. Ventral valve moderately gibbous; arcuate, compressed towards the cardinal extremities. Mesial sinus of moderate width and depth; rounded or slightly flattened on the bottom; umbo prominent; beak small, neatly curved over a wide triangular fissure, and reaching to within half a line of the umbo of the opposite valve; area concave, sub-linear, a little wider on each side near the center. Dorsal valve regularly convex, a little gibbous in the middle and flattened or sometimes slightly concave at the cardinal extremities. Mesial fold rather narrow, rounded, prominent and strongly defined, sometimes a little flattened on the middle. The surface is marked by six and rarely seven strongly rounded ribs on each side of the mesial fold or sinus. The ribs gradually decrease in size and prominence from the center; and the outer ones are often scarcely elevated in young or medium-sized individuals. The entire surface is marked by lamellose, concentric striae, giving a papillose or sub-fimbriate aspect at their junction; it usually happens, however, that the surface is smooth from partial exfoliation. (Hall.) This species has usually a width of one inch to one inch and a quarter, and a length of one-half to three-fourths of...
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Product details

  • Paperback | 106 pages
  • 189 x 246 x 6mm | 204g
  • United States
  • English
  • black & white illustrations
  • 123681214X
  • 9781236812148