Report Volume 57, PT. 3

Report Volume 57, PT. 3

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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. 1905 edition. Excerpt: frequently attained by interlocking of the ends of the plications along the dorsal line. (Ontaria, Lunulicardium, etc.)1 'The minute planktonic shell described by Simroth asPlanktomya henseni has on the hinge such denticulations as are shown by Buchiola and it seems probable that The convergence of these shells is a consequence of uniform physical conditions, and it has as its result the obliteration of original differences and ancestral generic characters. Hence the determination of phylogeny herein is rendered extremely difficult. Some are doubtless Dimyarians with cardioid affinities (Ontaria, Buchiola, Praecardium), others appear to be allied to the aviculoids and Monomyarians (Posidonia, Kochia, Loxopteria and probably Lunulicardium, Honeoyea, Pterochaenia). The tenuity of the shell rarely permits any indication of muscular scars. In Lunulicardium, Honeoyea and Pterochaenia ontogeny shows that the' primitive shell is simple and veneriform in outline, the great hiatus a wholly secondary development. OTHER COMPONENTS OF THE FAUNA The Pteropods are represented by myriads of individuals but only a few species. The Gastropods are more abundant in species, the predominant genera being Loxonema, Phragmostoma, Bellerophon, Tropidocyclus, Palaeotrochus and Pleurotomaria, all of thin shelled forms. Of the Brachiopods there are few, and these are seldom to be found in association with the characteristic members of the fauna. The only forms known are a Chonetes, a Crania, a small Productella, and three species of Lingula; all are rare and quite certainly survivors of the replaced Hamilton or interlopers from the adjoining Ithaca fauna. Of the Corals none are known save species of Aulopora found incrusting the dead shells fallen to the bottom, ...
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Product details

  • Paperback
  • 189 x 246 x 7mm | 240g
  • United States
  • English
  • black & white illustrations
  • 123689040X
  • 9781236890405