Pl. [1], Fig. 22.
HYALODISCUS RADIATUS VAR. ARCTICA GRUN.
Valve with radiating puncta from a rather small umbilicus, the rays interspersed with short, dark lines, having the appearance of spines, at irregular intervals. Margin broad, striated.
Pyxidicula radiata O'Meara.
The Philadelphia form corresponds exactly to Grunow's variety which has closer puncta than the type form.
Blue clay. Rather rare.
Pl. [1], Fig. 21.
HYALODISCUS SCOTICUS (KUETZ.) GRUN.
Valve small, with puncta about 24 in 10 µ, appearing hyaline.
De Toni remarks that it resembles a small form of H. subtilis which occurs north and south of our limits and is yet likely to be recorded.