Pl. [13], Fig. 18.
EUNOTIA BIDENTULA WM. SM.
Valve with straight ventral margin, and with two undulations on the dorsum; apices large, rounded.
May's Landing, N. J. Rare.
Pl. [13], Fig. 20 (not Schumann's form, which has angular crenæ).
EUNOTIA FORMICA EHR. VAR.?
Valve turgid in the middle and at the apices which are unilaterally truncate.
Pensauken, N. J. (artesian well).
Pl. [13], Fig. 26 (not a typical form).
The following are forms which appear to be indeterminate, or, in any case, are scarcely worthy of distinction by specific names, as might be said of others of the innumerable variations of this genus: