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Species / Anchura Grouti

Anchura Grouti


Original description of Anchura grouti by Bergquist, 1944:

  • "Shell a little more than medium-sized; spire accuminate, whorls seven or more, slightly convex, closely appressed, increasing gradually in size; apex broken off on all specimens; suture slightly impressed ; body whorl of shell convex, rounded in front and merged into a short anterior canal, which is broken on all specimens; inner aperture (seen from internal molds) broad, lenticular, notched in front for canal; outer lip thickened, expanded into a wide appendage, which on a large cotype extends for about 15 mm. and then curves upwards from the straight posterior margin into a long sharp spurlike projection, which is divergent to the shell axis; tip about at height of second whorl above body whorl; posterior commissure of body whorl extended backward upon the penultimate; a deep groove occurs above midheight on inner wall of outer lip, extending from aperture upwards on posterior extension of lip; this is indicated by a sharp keel on internal molds and a pronounced ridge on squeeze from external maids. Spire sculptured by curved axial ribs crossed by spiral ridges, giving a somewhat nodular effect; some external molds indicate that the axial ribs are lacking on the first three or four whorls and only a strong revolving line is seen along the suture (lack of axial ribs may in part be due to faulty preservation but seems to be quite prevalent); only spiral ridges occur on body whorl and these continue to deflection of wing, strongest development being on the midportion with a medial ridge continuing to tip of wing, the others are replaced by prominent growth lines from backward deflection of wing to the end. Internal molds most common, having deeply impressed sutures where shell was greatly thickened; whorls not always appressed in early part and are convex outward, later whorls sometimes slightly fiattened; surface smooth, internal thickening of shell apparently obliterated all external markings; columellar cavity broad and smooth."

Locus typicus: Hill Annex mine, Calumet, Itasca County, Minnesota, USA

Stratum typicum: Coleraine Formation, Cenomanian, upper Cretaceous

Anchura grouti Bergquist, 1944; Coleraine Formation, Cenomanian, upper Cretaceous; Mesabi Iron Range, Minnesota, USA; 25 mm; Coll. Philippe Simonet


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