AULISCUS CÆLATUS BAIL.
Valve elliptical or subcircular, with radiating costæ, more evident around the median areas and at the border, converging toward the processes, with intermediate punctate radiating lines. Central space rounded or irregular. Processes circular.
A. sculptus has coarser costæ and the interspaces are hyaline, or apparently so, while in A. cælatus the punctate striæ between the costæ are more evident.
Blue clay. Not uncommon.
Pl. [5], Fig. 4.
Fig. 7 is a small, indefinite form intermediate between A. sculptus and A. cælatus. The numerous variations in this genus make it difficult to satisfactorily differentiate the species. The size of the four above described varies from 40 to 150 µ.
Pseudauliscus A. S. (1875) and Leuduger-Fortmorel (1879)
Valve circular or subcircular, nearly flat or depressed at the centre. Central space not evident. Processes circular, with narrow border, near the circumference. Border narrow, striated. Markings granular, radiating, sometimes interspersed with striæ and apiculi.
Differs from Auliscus chiefly in the absence of a central space and costæ.
PSEUDAULISCUS RADIATUS (BAIL.) RATTR.