Pl. [1], Figs. 18 and 19.
Hyalodiscus Ehr. (1845)
(hyalos, transparent, and discus, a disc)
Frustules spheroidal; valve with a flattened, irregularly punctate umbilicus from which proceed radiating or decussating lines of fine puncta.
ANALYSIS OF SPECIES
| Valves divided into sectors | stelliger |
| Valves not divided but interrupted by short dark lines at intervals | radiatus |
| Valves with very fine puncta | scoticus |
HYALODISCUS STELLIGER BAIL.
Valve with puncta in oblique decussating rows which, by reason of the difference in obliquity, form numerous sectors. Umbilicus irregular, with scattered, coarse puncta. Margin wide, striated.
Podosira maculata Wm. Sm.
Blue clay. Not common.