Shell minute, globose-conic to conic, solidly formed, but rather thin; spire obtusely pointed, its slopes straight to weakly arcuate; whorls convex, the last well-rounded; suture deep; aperture a little more than half as high as the shell, ovate-pyriform, angulate posteriorly; lip sharp, reinforced anteriorly by an almost rib'like thickening within, which passes directly into the thickened and flattened columellar flare, this flare nearly covering the umbilicus or in some cases so strongly and perfectly appressed over it as to occlude its last vestige; columellar flare in its turn passing into the rather heavy parietal callus which then thins out to its connection with the outer lip, though a truly free peritreme in this region was observed in none of the specimens. Surface in general smooth except for the fine sharp growthstriae, although in some lights very faint indications of a minute spiral striation seem to be visible. Color Mummy Brown. Operculum paucispiral, the nucleus at first closely and regularly wound, but in its final turn expanding widely.
Radula with seven series of teeth, the medians squarish, minutely 5'denticulate apically, the sharp central denticle much the largest, and with three tiny oblique rounded denticulations close together on either side of the basal portion below the main series; admedians elongate, with about five small denticulations on the cutting edge, of which the central is the largest; second laterals similar, with four or five sharp denticles of which two are larger than the others; marginals thin, ovately expanded, the very delicate cutting edge finely nicked into numerous exceedingly minute denticulations.
Dimensions: of largest shell, alt. 2.88, diam. 1.96, alt. aperture 1.48, diam. aperture 1.15 mm., whorls 4.5; of holotype, alt. 2.66, diam. 1.92, alt. aperture 1.33, diam. aperture 1.11 mm., whorls 4.7.
Holotype: Cat. No. 7849 Stanford University Paleo. Type'Collection.
Type-Locality: Bad Water, elev. —279.6 It., Death Valley, Inyo County, California; Allyn G. Smith coll., 22 Feb. 1937.

By what I managed to make out from my rather imperfect radular preparations I was at first considerably confounded, as I could not correlate it in the least with the account and figure of the dentition of Assiminea grayana given by Gray (1857:87, fig. 48) after Loven, but more recently I was fortunate enough to look up the matter in Fischer's Manuel (1885:738, fig. 507) where a widely different radula is attributed to the same species on the weighty authority of Troschel. The two cannot possibly represent the same thing, but whereas the radula of the Death Valley species bears little resemblance to that of Loven, its similarity to that of Troschel in all particulars of generic significance is striking.
Accepting this generic allocation, we find our landlocked form to differ principally from A. californica (Tryon 1865), the only other Californian species hitherto recognised, in its much more robust outline, lower and much less sharply conical spire, more convex whorls, more capacious and strongly rounded body whorl, occasional umbilical chink, and larger aperture. The growthlines and axial color marks are also somewhat stronger.
The Bad Water shells are often covered with a blackish (algae) incrustation, and in addition more or less of a whitish saline deposit. The specific name suggested is from the L. infimus, deepest, and has reference to the unique site.

Type-Locality: Bad Water, elev. —279.6 It., Death Valley, Inyo County, California; Allyn G. Smith coll., 22 Feb. 1937.
Remarks: Bad Water is the drainless, below sea-level sump which occupies the lowest point in Death Valley and therefore in the Hemisphere. The waters are heavily saline, in much of the pool to the point of saturation, with the various associated solutes crystallising out in plates and crusts, in the very crevices of which the living snails may be collected, as well as from amongst the roots of the halophile plant, Salicornia, and the (presumably) less saline entering seepage.