FRAGILARIA CONSTRUENS (EHR.) GRUN.
Valve in general outline lanceolate, with produced apices; pseudoraphe lanceolate, distinct or broad; striæ subtle, 15 in 10 µ. L. of valve, 10-45 µ.
Staurosira construens Ehr.
Odontidium tabellaria Wm. Sm.
Blue clay.
Pl. [10], Fig. 30.
FRAGILARIA PARASITICA (WM. SM.)
Frustules solitary or in twos. Valve lanceolate, sometimes constricted in the middle; pseudoraphe wide, lanceolate; striæ subtle. Parasitic on other diatoms.
Odontidium parasiticum Wm. Sm.
Not common. Media (Palmer).