Species: Vinlandostrophia colbiensis (Foerste, 1910)
- 1910 Platystrophia colbiensis Foerste, Bull. Sci. Lab. Denison Univ., vol. 16, p. 55, pl. 4, figs. 2A-B.
- 1914 Platystrophia colbiensis Foerste, Journ. Cincinnati Soc. Nat. Hist., vol. 21, p. 131.
- 1919 Platystrophia colbiensis McEwan, Preceedings of the National Museum, vol. 56, p. 414, pl. 44, figs. 8-11.
Map point data provided by iDigBio.
- M6 (Lower Catheys)
- C1 (Upper Catheys, Clays Ferry)
Identification in Hand Sample
- Four plications on the fold, three on the sinus
- Lateral plications vary from 8-11
- Hinge line greatest width of the shell or a little less
- Width around 20-22 mm
- Slightly compressed fold with a shallow sinus
Vinlandostrophia colbiensis from the McMillan Formation of Georgetown Ohio (OUIP 614)
Brame (pers. comm., 2013):
- Low fold, 4 plications on fold, 3 on sinus; hinge line greatest width of shell
- I have discovered no practical way to distinguish immature specimens of the Saturday Mountain species from P. amoena McEwan, but the adults are readily distinguished by the greater number of flank costae, larger size, and relatively higher fold. P.colbiensis Foerste is very similar in outline. P. colbiensis has a fold even lower than those of immature specimens of the Saturday Mountain species.
- A small Platystrophia with only moderately elevated and not strongly compressed fold and shallow sinus. Plications 4 on the fold, 3 in the sinus, subequal in size. Lateral plications 8-10. Hinge line usually a little less than greatest width of shell. Width 21-22 mm., length about 0.8 width.
- In the Upper Trenton of Kentucky Tennessee occurs the species which Doctor Foerste has described as Platystrophia colbiensis the fold is slightly elevated and slightly compressed; the sinus is shallow. Four subequal plications occupy the fold; they have originated by the bifurcation of the two primary plications at the beak. There are three subequal plications in the sinus; one is primary and occupies a median position; two are lateral, secondary plications which are implanted on the slopes of the sinus at about 1.5 mm from the beak. There are 9 to 11 plications on the lateral slopes. Young specimens have subequally convex valves, but the brachial valve of older specimens is quite ventricose.
- This species is larger than Playstrophia amoena new species and the fold is slightly compressed, while the fold of that species becomes progressively wider as it approaches the frontal margin.
- Measurements. 20.6 mm along the hinge lie, 21.6 mm wide across the middle, 15.3 mm high, 14.4 mm thick, 9 mm sinal width, 6.5 mm sinal depth, 2 mm fold depth.
- Occurence. Trenton group: Cynthiana limestone: Between Colby and Winchester, Paris, Lexington, Frankfort, etc., Kentucky. Catheys formation: Edgefield Junction and Nashville, Tennessee.
- Plesiotypes. Cat. Nos. 34231, 48614, U.S.N.M.
- In the Cynthiana formation, between Colby and Winchester, in Kentucky, a small form of Platystrophia occurs in which the median fold is only moderately elevated, and not strongly compressed laterally, while the sinus is broad and shallow. Four plications occupy the fold, and three occur in the sinus. The number of lateral plications on each side of the fold varies usually from 8 to 9. The hinge-line may equal the width of the shell across the middle, but usually is a little shorter. The convexity of the shell is considerable, but rarely enough to be called gibbous. Owing to the small elevation of the fold, the brachial valve has a more evenly convex appearance than the small forms of Platystrophia occurring in the Mount Hope bed, and described by Meek under the term Platystrophia profundo-sulcata (Ohio Paleontology, vol. 1, plate 10, fig. 2 a-d). The length of a typical specimen is 13.5 mm.; the width, 19 mm.; the thickness through the valves, 12 mm.; the elevation of the fold above the general convexity, slightly over one millimeter.