Palaeontographical Society Monographs Volume 42, Nos. 198-203

Palaeontographical Society Monographs Volume 42, Nos. 198-203

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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. 1889 edition. Excerpt: ...Lioc. 0 palinum (Reinecke) its coarser ribbing and very concave umbilicus separate it specifically; from any forms of Ludwigia, the mode of ribbing and the difference in the suture-line separate it generically. The more minute differences which distinguish it from its varieties will be best understood by reference to pp. 66, 67, 69. It is singular that in spite of the frequency with which this species occurs, yet from the year 1815, the date which Sowerby's plate bears, until the year 1881, when my father figured a variety of it, no approach to any correctly identified specimens of Sowerby's species had been figured in England, nor, I believe, on the Continent. The regularly hollow umbilicus, which is mentioned by Sowerby, seems to have been either ignored or not noticed by those who have referred to this species; and, so far as my experience goes, the identification of this shell in both public and private collections leaves much to be desired. The name Ammonites conoavus is given, for some reason, to a shell or a whole series of forms from the Upper Lias, and seldom to our species from the Inferior Oolite. Probably d'Orbigny and Dumortier are to a certain extent answerable for this. The form from the Upper Lias figured by d'Orbigny under the name Am. concavus (' Terr. Jurass. Ceph., ' pl. 116) is referred by Dr. Vllright3 to Am. Lythensis, Young and Bird; and by Dr. Hang, with a query, to Am. compactilis, Simpson. At any rate it differs totally from Sowerby's Am. concavus in suture-line and ribbing, also in having a straight or slightly convex inner margin, and an open umbilicus.' MM. Chapuis and Dewalque also figure under the name Am. concavus, Sowerby, a species which appears more

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  • Paperback | 138 pages
  • 189 x 246 x 8mm | 259g
  • United States
  • English
  • black & white illustrations
  • 1236858360
  • 9781236858368