Formerly: Plectambonites rugosa (Foerste)
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Map point data provided by iDigBio.
C1 Sequence (McMicken, Southgate, Economy, Fulton)
Identificiation in Hand Sample
- Small size
- Sub-elliptical shape
- Lack of accessory teeth and hinge line denticles
- Raised muscle platform
Sowerbyella rugosa from Edenian formation of Campbell County, Kentucky (OUIP 142)
- (Speaking on Sowerbyella sericea) Wrinkles on the pedicle area, and possibly the undulation of the hinge line may be due to the compression of the specimen in a direction at right angles to the cardinal line; but on the interior of the brachial valve below the level of the hinge-line there are distinct ridges and furrows which appear to be continuous with the undulation of the hinge line. Similar structures are seen in Plectambonites rugosa from the Eden formation of Cincinnati, Ohio, which were attributed by James to a crenulation of the hinge line, have been discussed by A.F. Foerste, who remarks that it ‘is connected not with any actual wrinkling of the hinge area… but with the undulating surface of deposition of the shell material along the linear callosities lining the interior of the valves immediately within the hinge area.’ It is described as follows: ‘The interior of the brachial valve is slightly thickened along the hinge line, this thickening being narrowly linear… In many specimens this interior thickening along the hinge line is crossed by a series of minute transverse ridges, which, however, do not intrude upon the hinge area. In the case of the pedicle valve, a simialr series of minute transverse ridges is seen upon the linear callosity filling in the space between the hinge-area and the immediately underlying part of the shell. The shell material composing these transverse ridges is deposited by the mantle in an undulating manner…’ This explanation of the structure agrees entirely with the Author’s observations on British specimens from the Ordovician rocks.
- As regard to its internal characters, Plectambonites (Sowerbyella) rugosa from the Eden beds seems to be closely allied to S. sericea.