Palaeontographical Society Monographs Volume 48, Nos. 226-229

Palaeontographical Society Monographs Volume 48, Nos. 226-229

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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. 1894 edition. Excerpt: ...Plate VII, figs. 16--2-3; Plate XI, figs. 1, 2. Spefiific Chamctews-.--Shape variable, The anterior end is moderately convex, s its border circularly rounded. but more or less subquadrate and flattened. hort but deep in a dorso-ventral direction; The inferior border is rounded in front, y. The posterior part of the shell is narrowed The umbones appear to rise gradually from the whole surface of the shell, and are blunt, raised above the hinge-line; excavated anteriorly, and thinned internally by the encroachment of the lunule, which is moderately deep, widens anteriorly, and is roughly marked by striae continuous with the lines of growth which pass into it from the surface of the shell. The external ligament is prominent and erect, extending half the way from the umbones to the posterior end. The hinge-line is slightly arched. Hinge-plate triangular as in O'. acuta, the normal form; but, owing to the more quadrate and stumpy form of the shell, this part of the plate, posterior to the cardinal tooth, is placed at an obtuse angle to the anterior portion. Valves compressed with an almost obsolete, broad, oblique sinus, most apparent at the lower border. The posterior slope is dilated and obtuse. Shell thick. Muscle-scars normal. The surface is rough with coarse lines of growth. Periostracum thick and much wrinkled. 35 mm. Dorso-ventrally 25 mm. Laterally 16 mm. L0oalities.--The roof of the Ten-fo0t.Coa1, and-the horizon of the Cockshead Rock, Hulme Colliery. Ivy House Colliery, Bucknall. Whitfield Colliery. All in the Lower Coal-measures of North Stafibrdshire; Middle Coal-measures of Oldham. 's species appears to be less variable than most; and although fig. 22, Pl. VII, appears to differ in form from the others, it will be noted more

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  • Paperback | 92 pages
  • 189 x 246 x 5mm | 181g
  • United States
  • English
  • black & white illustrations
  • 1236756576
  • 9781236756572