The Riverside Natural History Volume 1

The Riverside Natural History Volume 1

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This 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. 1888 edition. Excerpt: ...arms, there are but two rows at the extremity. It greatly resembles an Ophidiaster in general appearance. The small size of the sucking-discs of the water-feet, and the general aspect of the animals, suggest that the genus should be placed with the Astropectinidae, near to Luidia. Caulaster is a singular star-fish, furnished with a peduncle in the centre of the disc, suggestive of the centro-dorsal tubercle of a Comatula. It was taken by the French exploring expedition. i: v. The Sea-TJrchins are cchinoderms without arms and without a stalk. They rrrt)protected externally by a calcareous test, composed of plates known as the coronal plates. These plates form ten distinct areas, five of which are perforated with pores for the exit of the suckers, and are known as the ambulacral areas, while the five intermediate areas bear no suckers, and are known as interambulacral. The variations in the form and size of these plates, and of the areas they compose, give rise to the varying shapes of the different genera. The mouth is always situated upon the lower or actinal aspect, which is applied in progression to the surface upon which the animal moves; but the position of the anus varies in different families. The surface of the plates, except where the pores are situated, is covered with spines, which occur upon every species of echinoid, but vary greatly in their number, structure, and size, so that they form one of the best characters by which species can be distinguished. There seems at first sight to be little resemblance between the huge bat-like spines of Heterocentrotus, the sharp, hollow, brittle spines of the Diadematidse, the solidfluted spines of the Echinidffi, and the slender, delicate spines, usually short, but sometimes long and silky, of...show more

Product details

  • Paperback | 248 pages
  • 189 x 246 x 13mm | 449g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 123660184X
  • 9781236601841