Memoir Volume 3-4

Memoir Volume 3-4

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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. 1900 edition. Excerpt: ...and the pygidial pleura simple. The latter is believed to be limited to Mesodevonic faunas (P. rana, Hamilton, P. latifrons, Eifelian), while the former is widely disseminated as a characteristic Paleodevonic group. To this belong the Helderbergian species. Of Acidaspis we have two species; A. tuberculata is related to the Onondaga A. callicera. The remarkable A. hamata (genus Dicranuru s) with long, recurved cervical horns, finds its only known analogue and almost specific identity in the A. monstrosa, Barrande, of the etage G (Paleodevonic). Lichas is represented by L. pustulosus, the most abundant species, which seems to indicate a type of subgeneric structure not elsewhere presented. L. cons an guineus belongs to the subgenus Arges and has species both in the Siluric and Devonic. The single species of Proetus (P. protuberans) in the Helderbergian of New York is of rare occurrence. In type of structure it conforms throughout to the series P. conradi, Oriskany, P. angusti-frons, Schoharie grit, P. clarus, Onondaga limestone and P. rowi of the Hamilton group. C ordania makes its earliest appearance in the Helderbergian, and is represented in the Oriskany, Schoharie grit, Onondaga and Hamilton faunas. O y p h as p i s c o e 1 e b s (the only species) is closely allied to C. min us c u l u s of the Oriskany and Onondaga. Gastropods. This group is characterized by an immense development of the genus P l a t y c e r a s, which has been but sparingly represented in the Siluric faunas, but attains its numeric climax in species here and in the Onondaga and Hamilton. The prevalence of these forms is one of the most striking characters of " Hercynian " faunas, and Barrois has suggested that they may with propriety be designated by the...
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Product details

  • Paperback | 58 pages
  • 189 x 246 x 3mm | 122g
  • United States
  • English
  • black & white illustrations
  • 1236932862
  • 9781236932860