Mesozoic Fossils

Seitenzahl:

106

Gewicht:

168 g

Erschienen bei:

Cambridge Scholars Publishing

Kurzbeschreibung

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: reflected, and is continuous above with a flat, expanded, semiovate callus, which spreads over nearly the whole of the columellar side of the mouth and sometimes covers a small portion of the last whorl but one. At the junction of the outer with the inner or columellar lip there is a rather deep and sub-angular notch or " insinuation," whose centre is exactly in a line with the suture. There are three large, prominent, oblique, spiral plaits on the columella, which are parallel with each other, and about three lines apart at their summits. The upper or posterior plait is placed near the middle of the aperture, on its inner side, and the lowest, which is the least prominent of the three, is situated half way between the posterior plait and the base of the shell. On the body whorl the surface markings consist of eighteen or nineteen revolving raised lines or narrow ridges, which are interrupted and made nodulous by their being crossed by obscure and low, but rather broad, transverse folds, and coarse stria! of growth. F. Navarroensis is probably only a varietal form of the Valuta elongata of D'Orbigny and other authors, which Stoliczka places in Schumacher's subgenus Fulguraria. The difference between the two nominal species practically amounts to this, that in some specimens of F. elongata the body whorl is more constricted posteriorly than it is known to be in F. Navarroensis, and that the transverse ribbing or plication of the surface is strongest in the former. A glance at Stoliczka's illustrations of Indian examples of F. elongata, however, will be sufficient to shew that these distinctions are not much to be relied upon as affording good specific characters. Nine individuals of this species are represented on Plate 7 of the second volume of the Palceontologia Indica, and fo...

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Mehr von:  Geological Survey of Canada, Cambridge Scholars Publishing