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Polyptychites

Polyptichites is the perisphictacean ammonite genus from the Lower Cretaceous of Russia. The shell is subinvolute and coarsely ribbed; ribs bifurcate or trifurcate mid or low on the flanks and cross over the rounded venter. The umbilicus is relatively small and deep. Outer whorls partially envelop the previous leaving a fairly deeply impressed dorsum.