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OverviewThis historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1920 Excerpt: ...individual. It would seem, therefore, that this genus, evolving from a Silurian form like Sagenocrinus or Temnocrinus, underwent its final transformation in the Burlington limestone by taking on an additional primary plate in each ray; and that this was accomplished by a specific change far more complete and decisive than we find in some other cases where the modification was going on in the Devonian. Doubtless if we had all the stages of this development through the Devonian we should see phases of individual variation; but the final stage became firmly established in the genus, with one species tenaciously holding on to its Silurian type of ray structure. It is singular that with this apparently straight line of derivation, no trace of this type has been found in the prolific crinoidal deposits of the Lower Burlington beds at the same locality. We must remember, however, in this and all similar cases what we are constantly prone to overlook--that our collections, even from these prolific and well searched formations, represent only a mere atom of what actually existed during their epoch, or was deposited in their sediments. Types. Hall's original is in the University of Chicago; the other specimens figured are in my own collection. The original of figure 2, PIate XXV, one of the finest specimens known, was found by Mr. J. O. Beebe, a most zealous and intelligent Burlington collector, who presented it to me for use irl this work. Horizon and locality. Lower Carboniferous, Upper Burlington limestone; Burlington, Iowa; Henderson County, Illinois: and Washington County, Indiana. Forbesiocrinus burlingtonensis n. sp. Plate XXVI, figs. 3-5 I have separated under this name those specimens occurring in the Burlington rocks which have three primihrachs. The descri... Full Product DetailsAuthor: Frank Springer , Smithsonian InstitutionPublisher: Sagwan Press Imprint: Sagwan Press Dimensions: Width: 15.60cm , Height: 2.60cm , Length: 23.40cm Weight: 0.694kg ISBN: 9781377269313ISBN 10: 1377269310 Pages: 502 Publication Date: 09 February 2018 Audience: General/trade , General Format: Paperback Publisher's Status: Active Availability: In Print  This item will be ordered in for you from one of our suppliers. Upon receipt, we will promptly dispatch it out to you. For in store availability, please contact us. Table of ContentsReviewsAuthor InformationTab Content 6Author Website:Countries AvailableAll regions |
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