Original description of Nudivagus? cooperensis by Stephenson, 1941:
- "Shell large, simple, turreted, spiral angle about 30 degrees. Whorls 6 as preserved, with 3 or 4 missing at the apex. Whorls very broadly convex on the side, slightly constricted below the suture. Suture closely appressed. Surface smooth to the naked eye, but under the microscope fine, closely spaced spiral lines appear in a band below the suture, and similar lines can be faintly seen elsewhere; the apparent absence of these lines on parts of the surface is probably due to the poor state of preservation of the shell. The periphery of the body whorl is broadly rounded; on the side of the body whorl just back of the aperture the base descends gradually to the beginning of the anterior canal where there is a sharp constriction. The aperture is elongated, is acutely angular at the rear, and passes into an elongated canal in front; the latter is broken away, but in the type species from Coon Creek, Tennessee, it is narrow, of moderate length, and noticeably sinuous. The outer lip is broken away; the inner lip is imperfect, but is broadly excavated and forms a thin coating of callus."
Locus typicus: 2/5 mile north of Cooper, Delta County, Texas, USA
Stratum typicum: Neylandville marl, Navarro Group, Maastrichtian, Cretaceous
Holotype: Coll. U.S.N.M. no. 76900; height 57= mm, diameter about 20.5 mm.
Nudivagus ? cooperensis in Stephenson, 1941, pl. 54, fig. 11, 12
- Image courtesy The University of Texas at Austin