Bulletin - United States National Museum, Volume 91

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Smithsonian Institution Press, 1915 - Science
 

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Page 90 - Nuclear whorls deeply immersed in the first of the succeeding turns, above which the tilted edge of the last volution only projects. Postnuclear whorls...
Page 15 - The postnuclear whorls are moderately rounded and crossed by rather retractively slanting axial ribs, which are about as wide as the spaces that separate them. Of these ribs 19 occur on the last turn behind the varix, 29 on the penultimate, 31 on the third from the last, 27 on the fourth from the last, 26 on the fifth from the last and 12 on the ribbed portion of the seventh whorl. The parts preceding this are not definitely ribbed. The varix behind the peristome...
Page 167 - ... parietal wall covered with a thick callus, which renders the peritreme complete. The unique type, which was dredged by Mr.
Page 128 - ALFREDENSIS, new species. Plate 21, fig. 8. Shell elongate-conic, white. The nucleus consists of a single turn which appears to be smooth. The succeeding turn is well rounded, the next, strongly shouldered on the middle, while the last is slightly concave immediately below the suture, and the rest well rounded. The second whorl is marked with six slender spiral cords, which are about as wide as the spaces that separate them. On the following turn a broad cord appears at the appressed summit and four...
Page iii - The majority of the volumes are octavo in size, but a quarto size has been adopted in a few instances in which large plates were regarded as indispensable.
Page 106 - The spaces inclosed by the, ribs and cords form oval pits, the long axis of which coincides with the spiral sculpture. Sutures channeled. Periphery of the last whorl marked by a moderately broad groove, which is crossed by the continuation of the axial ribs which terminate at the posterior edge of the first basal keel. Base of the last whorl well rounded, marked by six spiral keels which grow successively weaker from the periphery to the umbilical region. The broad spaces between these keels are...
Page 125 - Posterior angle obtuse; outer lip thick; inner lip very thick, curved and appressed to the base; parietal wall covered with a thick callus, which joins the posterior angle of the aperture to the inner lip.
Page 131 - Base of the last whorl well rounded, marked by five spiral cords, which grow successively a little weaker from the periphery to the umbilical area. The spaces between these cords are marked by slender spiral threads, which correspond to the ribs on the spire. Aperture oval, posterior angle...
Page 92 - Aperture oval ; posterior angle acute ; outer lip thin; columella decidedly curved and reflected, provided with a strong oblique fold at its insertion ; parietal wall glazed with a moderately thick callus.
Page 201 - Postnuclear whorls 2.9 in the specimen figured, strongly inflated. The first turn at its junction with the nuclear whorl marked by almost axial riblets, which slant retractively and which gradually become lessened in strength and on the last turn appear as fine axial threads, which are about as wide as the spaces that separate them. These whorls are also marked by faintly incised spiral lines which give to the surface an obscurely granulose effect when viewed under high magnification.

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