Memoirs of the Museum of Comparative Zool Ogy at Harvard College Volume 42

Memoirs of the Museum of Comparative Zool Ogy at Harvard College Volume 42

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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. 1915 edition. Excerpt: ...by their shape alone, the larger (largest) kind of small micramphidiscs should, indeed, be considered as belonging to the large micramphidiscs. Since, however, in the smaller (A, B, C, E) or smallest and intermediate (F) kinds of small micramphidiscs the relative breadth of the anchors decreases with the increase in the size (length) of the spicules, since in a few exceptional spicules of this kind the anchors are quite as slender as in the larger (largest) kind, and since they are, in the forms where they occur, separated biometrically much more clearly from the larger micramphidiscs than from the smaller kind of the small micramphidiscs, I provisionally place them in the latter group. The small micramphidiscs of form A (Plate 44, fig. 17d; Plate 45, figs. 4045; Plate 47, figs. 3, 4, 7-9) are 15-36 n long, most frequently about 18.3 n. The limit between the larger and the smaller kind lies at about 29 n. The shaft is straight or rarely bent, 0.6-1.4 n thick, cylindrical throughout, or slightly and gradually thickened in the middle. It is either quite smooth, or it bears near the centre an irregular cluster of a few spines, not over 0.5 M long, or it is covered with sparse, vertical, more rarely oblique, spines throughout. The anchors are 4-13 /i long, that is a quarter to a third of the whole spicule, and 4.7-9 n broad. They consist of fifteen or sixteen recurved teeth. In the larger kind of small micramphidiscs the proportion of the length to the breadth of the anchor is 100 to 58-75, on an average 100: 64; in the smaller kind 100 to 75-135, on an average 100: 93. It is to be noted that in the smaller small micramphidiscs the relative breadth of the anchor is, on the whole, in inverse proportion to their size (length). The curvature of...show more

Product details

  • Paperback | 154 pages
  • 189 x 246 x 8mm | 286g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236984382
  • 9781236984388