Memoirs Read Before the Boston Society of Natural History Volume 7

Memoirs Read Before the Boston Society of Natural History Volume 7

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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. 1912 edition. Excerpt: ...lanterns, also of the lanterns of young modern regular Echini. The teeth are grooved, meet in a point ventrally, and dorsally extend to a point just above the base of the foramen magnum, so that they are seen in side view. This is evidently the dorsal limit of the calcified portion of the tooth, beyond which the uncalcified portion would doubtless extend in life as in Strongylocentrotus (Plate 5, figs. 6, 9). The pyramids are very wide-angled, with a rather shallow foramen magnum. Hollows are on either side of the face view, in which the retractor muscles took origin; the sides of the pyramids are curved, admitting of relatively long interpyramidal muscles. The lateral wings of the pyramid are wide, as in Oligoporus (Plate 50, fig. 11), a resultant of the inclined angle of the lantern. A narrow epiphysis caps each half-pyramid, .seen in face view (Plate 27, fig. 6), and in dorsal view (Plate 27, fig. 5), it extends inward, narrowing toward the oesophageal cavity. A typical brace rests on and interlocks with the two adjacent epiphyses as shown in ventral, side, and dorsal views. The brace has the usual condyles and other outlines of modern regular Echini. In one area, D, of figure 5, a compass exists, slightly displaced, and apparently fragments of two other compasses in areas B and J. The compass is arched as usual, but shows no bifid distal end; probably it was worn off, but possibly no bifid tip existed, as in some Recent Echini. In the ventral view (Plate 27, fig. 4) the lantern is in part covered with the ambulacral plates 'of the peristome, which alone fill this area in the species and the family. It is interesting to see how near the lantern of this ancient type is to the character of the lantern in young modern regular Echini, .
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Product details

  • Paperback | 270 pages
  • 189 x 246 x 14mm | 485g
  • United States
  • English
  • black & white illustrations
  • 1236957210
  • 9781236957214