Fragilaria socia

Synedra socia nov. sp.

Valvis anguste lanceolatis, 16-42 µ longis, 3.5-4 µ latis, apicibus attenuato-rostratis, pseudo-nodule exentrico vel saepe marginem attingente, pseudoraphe angusta, striis 17 in 10 µ.

In outline, the longest specimen resembles that of Synedra rumpens var. familaris Grun. It differs from this in being somewhat wider (3.5-4 µ instead of 2-3 µ) which makes the diatom appear stouter. The striae have a morphology very similar to that found in Syndera acus var. angustissima Grun., i.e., more distinct, heavier. The central area generally extends to the margins, but in the smaller forms the area may become slightly unilateral. The shortened straie on the side of the central area are suggestive of Synedra vaucheriae Kütz. I have examined two different Kützing Decas #24, and the Synedra vaucheriae striae are coarser, and the striate side exhibits no swelling, i.e., is straight. Synedra socia forms the typical Synedra fascicles. It has been found in the Savannah River, a typical enriched eutrophic river. It reached maximum development in the later winter and early spring.

Type - Savannah River, Screven County, Georgia, Coll. R. Patrick, January 18, 1952 (A-G.C. 4036a).

• Basionym
  Synedra socia
• Author
  Wallace 1955
• Length Range
  16-42 µm
• Width
  3.5-4 µm
• Striae in 10µm
  17