Zygospira cincinnatiensis

• Pentagonal in shape
• Diagnostic lateral plications on either side of the fold, usually numbering 5
• Lateral margins are generally much compressed
• Generally less common but larger than Z. modesta with less plications
• More common bifurcation of the lateral plications of fold and sinus than Z.modesta
• More prominent fold and sinus than Z.modesta

• Usually 5 primary lateral plications on either side of fold

Davis (1998):

• the less common Z. cincinatiensis is larger than Z. modesta, pentagonal in shape, and has fewer plications; it occurs in the upper Kope and the Fairview

McFarland (1931):

• A comparatively large species with length, 8 or 9 to 14 mm., width, 1.2 length. It is distinguished from Z. modesta in addition to the larger size by the smaller number, hence coarser primary lateral plications (5-6 on each side), more common bifurcation of the lateral plications of fold and sinus and more prominent fold and sinus.

Foerste (1909):

• The specimens from the upper Fairmont, which are here regarded as typical, are distinguished from Zygrospira modesta by the small number of primary lateral plications, usually 5 on each side of the median fold. In consequence the plications appear larger, more angular, and more distant from each other. The more prominent median elevation on the pedicel valve is due chiefly to the larger size of the individuals. The four primary plications on the median fold and the intermediate grooves have very much the same appearance as in Zygospira modesta. While the bifurcation of the primary plications, or the intercalation of additional ones, is the chief character usually relied upon in diagnosing this species, too much weight must not be given to this feature, since it is not constant, and numerous specimens may be collected at the typical horizon, in which there is no evidence of bifurcation. Among the four primary plications on the median fold, it is the lateral plications, and not the two median plications which frequently are bifurcated. Bifurcation of one or two of the lateral plications on each side of the median fold is not rare. Occasionally, even the two median plications on the fold are bifurcated toward the anterior margin of the shell, or one or two small plications are inserted near the anterior end of the median groove. Some of these specimens attain a length of 13 mm. Only the larger specimens are likely to show evidence of frequent bifurcation.

Miller (1875):

• This variety or species differs from the last in its larger size, greater proportional breadth, more prominent mesial elevation, deeper furrow in the middle, deeper mesial sinus, and more spreading and coarser lateral plications. Its lateral margins are generally much compressed. Prof. Meek thinks it may be only a robust variety of Z. modesta. Found on the hills back of Cincinnati, associated with the modesta, at elevations from 250 to 400 feet above low water-mark.

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