Pl. [5], Fig. 6.
AULISCUS PRUINOSUS BAIL.
Valve elliptical, with distinct, interrupted, pruinose, irregular markings diverging in curved lines toward the circumference in the median part and converging toward the processes, interspersed with numerous darker markings having the appearance of apiculi. Central space nearly circular, sometimes with several granules. Processes large near the ends of the major axis and not oblique to it, or scarcely so, the edges with a crenulate border.
Blue clay. Rather rare.
Pl. [5], Fig. 8.
AULISCUS SCULPTUS (WM. SM.) RALFS
Valve elliptical or subcircular, median areas distinct, rounded, circumscribed by coarse distant costæ radiating near the border where they are more evident, and converging toward the processes. Central space rounded, sometimes indefinite. Processes, two, circular.
Typical specimens show wide, coarse, distant costæ, but, in some cases, the median areas are indistinctly outlined.
Blue clay.
Pl. [5], Fig. 5.