• Category
  • Length Range
    22-32 µm
  • Width Range
    4.6-5.6 µm
  • Striae in 10 µm



Valves are linear, with rounded ends. Striae are strongly radiate in the central part of the valve and strongly convergent at the ends. The striae are not visible under LM. The striae continue onto the valve mantle. The axial area is very narrow and the central ares is small and elliptic. The raphe is filiform, with proximal ends very close together and slightly bent to the primary side of the valve. The terminal raphe fissures are hooked to the secondary side of the valve and extend to the mantle. The upper surface of the valve is covered by a conopeum that merges with a fold formed at the valve face/mantle junction around most of the valve. At the apices the conopeum does not merge with the fold and thus, two openings at each apex are formed. The conopeum has small pores that form branching fascicles that are visible in LM along the raphe. These branching fascicles may be mistaken for the striae.


Original Description

Valve linear with rounded ends. Axial area narrow. Central area not differentiated from axial area. Striae parallel, thickened near the axial area, producing an apparent band on each side of the axial area. Striae very fine, difficult to resolve. Striae, 29-31 in 10 µ. Length, 24-31 µ (type, 29 µ). Breadth, 5-6 µ (type, 6 µ).

  • Basionym
    Navicula latelongitudinalis
  • Author
    R.M.Patrick 1959

Original Images

Nalatelo  Orig Ill001
Nalatelo  Orig Descr001

Cite This Page

Potapova, M. (2013). Fallacia latelongitudinalis. In Diatoms of North America. Retrieved July 24, 2024, from https://diatoms.org/species/fallacia_latelongitudinalis


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Fallacia latelongitudinalis from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.