Stauroneis staurolineata

Valves lanceolate, tapering to narrow-rostrate ends. Axial area linear, broadening at the ends. Fascia narrow, linear, crossed by conspicuous longitudinal hyaline ribs. Raphe linear, slightly broadened between valve center and ends. Proximal raphe-ends close, distal ends forking about 3 to 4 μ from valve ends at a sub-terminal nodule. One raphe branch elongate, hooking into the end. Striae radiate except at the ends where they become single puncta due to the thick longitudinal ribs extending into the ends. Longitudinal ribs approximately parallel, not conspicuously undulate, not interrupted at the fascia. Length--90-115 μ; width--15-17 μ; striae--16-17/10 μ; longitudinal ribs--9-11/10 μ.

Illustration specimen: ANSP-H.L.Sm. 502 (holotype). Type locality: New Hampshire, Carroll Co., Wolfboro. Recorded U.S. distribution: NEW HAMPSHIRE, Carroll Co., Wolfboro (ANSP-H.L.Sm. 502, Febiger 4466); Bemis Lake, fresh water, recent (?) (ANSP-GC 42822, 42823). PENNSYLVANIA, Philadelphia Co., Gray's Ferry, clay (ANSP-GC 42665, 43542, 53543).

This species is very closely related to S. stodderi Lewis. The most conspicuous features of this species are: 1) the continuation of longitudinal lines through the stauros area, 2) the sub-terminal nodule. For a more complete discussion of this see S. stodderi.

Cleve (1984, p. 110) described a Navicula stodderi var. insignis Grun. Ms, which probably belongs here as a variety. The Cleve & Möller preparation (ANSP-Cl&Möll. 187) has Grunow's taxon listed but it is not present anywhere on the slide.

As described by Cleve, the variety insignis has coarser longitudinal ribs (7-8/10 μ) and is considerably broader (21 μ side) than S. staurolineata. The position of the terminal nodules and the character of the axial longitudinal ribs near the central area is not definite from Cleve's data. It is, nevertheless, quite clear that the stauros is crossed by the longitudinal ribs thus eliminating it from S. stodderi.

This taxon and also S. stodderi are most unusual for Stauroneis in that they have quite thick longitudinal ribs or partitions similar to the ribs described for the genus Neidium (Hustedt, 1939, pp. 17-20) (Reimer, 1959a, pp. 2-3). Further study may show the necessity of their being transferred to another genus or placed under a new genus. The latter would be more likely for they certainly would not fit in the genus Neidium. The only likely place at present seems to be in Stauroneis. In my opinion a stauros can be demonstrated thus warranting such a conclusion.

• Basionym
  Stauroneis staurolineata
• Author
  Reimer 1961
• Length Range
  90-115 µm
• Width
  15-17 µm
• Striae in 10µm
  16-17