Geological Papers Volume 107

Geological Papers Volume 107

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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. 1907 edition. Excerpt: ...Me. Pterinea fasciculata Goldfuss var. occidentalis nov. See Pterinea fasciculata Goldfuss. Petrefacta Germaniae, 2: 137, pi. 129. fig. $, and Freeh. Devon. Aviculiden Deutschlands. 1891. p. 84, pi. 8, fig. 1; pi. 9, fig. 1-3. This extremely common shell is essentially a miniature of l. fasciculata Goldfuss. Though reduced in all its proportions and in the strength of its ornament yet it expresses excellently the characters of the German species. TJie valves are both convex, the left notably and the right but slightly. The left valve has the body well elevated above the posterior wing. This wing is sometimes more incurved at the margin and more extended at the point than in the figured German specimens but these features are variable in the Dalhousie shells. The body of the shell or direction of the crescence line is commonly more oblique than in Kuropean specimens but this is an expression due in some measure to mode of preservation, for examples occur here niite as erect as those referred to. The breadth of the byssal groove and emargination on the valve are also notable; together with the relative development of the anterior ear they are in full agreement with P. fasciculata. The surface of this valve is marked by coarsely fasciculated radial striae. The major ribs do not exceed five or six but these are widely separated on the body of the shell, the interspaces occupied by radii of lower order. On the posterior slope the striae are of uniform size and are visible on the wing. On the anterior wing there are two or three coarse riblets but the byssal sinus is deep and without radii. Crossing these elevated radial lines are fine crowded and elevated concentric lines giving all the surface except the byssal sinus a reticulate ornament....show more

Product details

  • Paperback | 104 pages
  • 189 x 246 x 6mm | 200g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236948319
  • 9781236948311