Studies in Evolution; Mainly Reprints of Occasional Papers Selected from the Publications of the Laboratory of Invertebrate Paleontology, Peabody Museum, Yale University

Studies in Evolution; Mainly Reprints of Occasional Papers Selected from the Publications of the Laboratory of Invertebrate Paleontology, Peabody Museum, Yale University

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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. 1901 edition. Excerpt: ...expansions from ventral mantle, and consequent production of deltidial plates filling delthyrium except at pedicle-opening. See figure 117. An examination of.the animal at this stage shows that the mantle lobes line only the interior of the valves proper. The exposed edges of the mantle are around the peripheries of the valves and also that portion of the ventral mantle border limiting the deltidial opening and passing along the sides of the pedicle at its base. The ventral mantle gradually extends from each side as two prolongations partially covering the opening and enveloping the proximal portion of the pedicle. As this is an extension of the shell-secreting surface of the mantle, there naturally results the formation of two plates within the deltidial area. Their structure is commonly punctate whenever the valves are punctate. These outgrowths or extensions of the mantle into the deltidial area finally touch and coalesce until, as in M. Jlavescens, the pedicle emerges through an opening in the ventral mantle, and pari passu the deltidial plates unite and limit the pedicleopening to the beak of the ventral valve. The latter process has been carefully described by Deslongchamps,6 Clarke, and the writer, s and need not be dwelt on here. Figures 119 and 120 of the beaks of T. septentrionalis and M. jlavescens with the shell removed show the relations of the ventral mantle to the pedicle, and the portions which secrete the deltidial plates. The deltidium and delthyrium are often simulated in the growth of the dorsal valve in genera having a high cardinal area in this valve. Orthis, Leptoma, Clitambonites, Spirifer, and Stricklandinia may be cited as examples. They cannot be properly correlated with similar parts in the ventral valve, for..show more

Product details

  • Paperback
  • 189 x 246 x 10mm | 331g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236863496
  • 9781236863492