Permoceras

Permoceras, the sole member of the Permoceratidae, is a coiled nautiloid with a smooth, compressed involute shell, whorls higher than wide, earlier whorls hidden from view. The venter is rounded as are the ventral and umbilical shoulders, the flanks flattened. The siphuncle is ventrally subcentral. The suture, which is most characteristic, has a d...
Found on http://en.wikipedia.org/wiki/Permoceras
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