ARCELLA VULGARIS. 139 
is compressed, its surface is parallel to the base and 
almost half its width. The lateral margins form six 
or eight obtusely-angular facets, the divisions of which 
are faintly distinguishable in face view; the neck is 
broadly mverted and extends upwards into the cavity 
of the test to about one third the distance separating 
the base from the crown. 
Dimensions: Diameter in face view averaging 100 
to 120 »; from base to crown in side view about 45 p. 
In Sphagnum from Dolgoch, Merionethshire, Aug., 
1905. 
This variety is one of the numerous forms figured 
by Leidy under the general name of Arcella vulgaris, 
but is so distinct, and so evidently a permanent form, 
that its separation as a variety approaching A. angulosa. 
is desirable. Penard figures it (loc. cit.) as a Huropean 
form of A. artocrea, but this species, according to 
Leidy, though pitted with surface-depressions, has an 
arched crown. G.S. West also (‘ Journ. Linn. Soe.,’ 
Zool., vol. xxvii) figures it thus. 
Arcella vulgaris var. compressa is rare. We have 
only met with it in Merionethshire. 
Fic. 28.—Arcella vulgaris var. compressa (face and lateral views, in 
outline). In Sphagnum from Dolgoch, Merionethshire. x 260. 
