A Manual of Palaeontology, for the Use of Students; With a General Introduction of the Principles of Palaentology Volume 1

A Manual of Palaeontology, for the Use of Students; With a General Introduction of the Principles of Palaentology Volume 1

By (author) 

List price: US$10.56

Currently unavailable

Add to wishlist

AbeBooks may have this title (opens in new window).

Try AbeBooks

Description

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: ...five large basals, with a single zone of radials, while interradials are wanting, with the exception of a single small anal plate. The arms are bifurcated, and the subdivisions unite with one another by means of lateral processes, thus giving rise to a network, perforated by numerous apertures (fig. 303). The Silurian genus Enal/ocrinur is nearly allied to Cratalocrinus, but the arms become free towards their extremities. 1'llmI'/y 7. It/11/zyocrz'ni'dcentse.--In this family the calyx is " dicyclic, ' but the three underbasals are small, and are mostly not visible externally. The radials articulate upon one another, and are united laterally by the perisomic plates of the disc. The arms are short, bifurcating, and often in contact laterally, thus forming an upward continuation of the calyx (fig. 304, A); while pinnules are apparently wanting. The disc had open ambulacral grooves, and was covered with perisomic plates, like that of a recent Crinoid. Its central part was occupied so as. to open the mouth to the 3;... (Arm Hall and M'C0y-) exterior. The members of this family are found in the Silurian, Devonian, and Carboniferous deposits. __The typical genera of the It/ll/lyo: r1'm'n'a'--sucli as Ir/il/ryocr1'nu.r itself (Silurian to Carboniferous), Lecanocrinus (Silurian and Devonian), and Me: pz'l0crinu: (Carboniferous)--are characterised generally by the imperfect separation of the calyx and arms, the latter being commonly in close apposition laterally (fig. 304, A). On the other hand, the genus Tr_zx0crinu.r (fig. 304, B) represents a section of the family--sometimes raised to the rank of a Separate family (Ta1'0e'r!'nl'r!'a')--in which the arms are well developed and repeatedly bifurcated. The species oshow more

Product details

  • Paperback | 264 pages
  • 189 x 246 x 14mm | 476g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236963067
  • 9781236963062