Shells with more or less elevated spires; closed coiled whorls except in senescent (phylogerontic) species. Whorls angular, generally with several carinae of which the central one forms a strong keel and is marked by an obtusely rounded peripheral “band” which is often marked with spirals of which the central one is heaviest. Umbilicus nearly always present. Outer lip notched but without slit. Ordovicic – Devonic.
Ulrich & Scofield (1897):
Height, of Loraine group specimens, 20 to 32 mm., of Richmond group specimens, 22 to 50 mm.; apical angle 70° to 80°. Volutions about six, the last equalling about two-thirds of the total height. Upper carina thick, near the suture, present on all volutions; lower carina nearly obsolete, represented by a broad swelling or low ridge, above which to the prominent peripheral band the surface is more or less concave. Inner lip very thick, almost or entirely covering the minute umbilicus, very broad and turned obliquely downward and forward in the basal half. Surface markings very strongly curved, unequal, on the whole not sharply defined.
Closely related to L. oweni, yet easily distinguished by the greatly thickened, broad and obliquely extended inner lip. The apical angle also is greater, and the lines of growth are more curved, especially at the base, while the upper carina does not fade away on the last volutions as in that species. The presence of this carina distinguishes it from the associated and otherwise similar L. multigrama Miller. L. medialis, which is usually much smaller, with the same number of volutions, a smaller apical angle and more distinct umbilicus, also has no such sutural carina.
