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Diatoms of the United States is now known as Diatoms of North America.
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SPECIES starting with "m"


Mastogloia albertii

  1. Valves elliptic-lanceolate
  2. Protracted apices
  3. Valvocopulae with locules
  4. Striae 15-18 in 10 µm

Symmetrical biraphid - Valves elliptic-lanceolate with protracted, broadly rounded apices. The raphe is filiform, becoming lateral at about ½ from the apices to the center. Striae are radiate and distinctly punctate.

Mastogloia calcarea

  1. Valve margins nearly parallel
  2. Apices rostrate
  3. Small central area, often asymmetric
  4. Raphe kinked near central area

Symmetrical biraphid - Valves normally linear-lanceolate. Apices normally rostrate. Central area small, commonly asymmetric, elliptic to irregular in shape. Raphe generally straight, but kinked near the central area. Proximal raphe ends deflected in the same direction. Striae punctate, slightly radiate, becoming almost parallel near the apices.

Mastogloia elliptica

  1. Partecta all of same size
  2. Striae uniseriate
  3. Raphe branches sinuous

Symmetrical biraphid - Valves are elliptic to linear-elliptic with bluntly rounded ends. Partecta are all the same size. Striae consist of single rows of coarse areolae. Raphe branches are sinuous (not straight).

Mastogloia grevillei

Mastogloia smithii var. grevillei

  1. Valve linear-lanceolate
  2. Raphe undulate
  3. Striae biseriate

Symmetrical biraphid - Valve linear-lanceolate with apices protracted and rounded. The raphe is lateral, reverse lateral about midway from the apices to the central area. Striae are radiate and biseriate.

Mastogloia lacustris

  1. Valves linear-lanceolate
  2. External proximal raphe ends enlarged
  3. Width 8-10 µm

Symmetrical biraphid - Valves linear-lanceolate, with margins slightly convex to nearly straight. The apices are bluntly produced. The raphe is straight and filiform, becoming lateral at about ½ the way between the apex and central area. The proximal raphe ends are enlarged. Striae are distinctly punctate and radiate, except at the apices where they are parallel.

Mastogloia pseudosmithii

  1. Valve elliptic-lanceolate
  2. Apices rostrate
  3. Raphe with median kink
  4. Striae slightly radiate

Symmetrical biraphid - Valves are elliptic-lanceolate. Apices are normally rostrate, becoming rounded in small cells. The central area is elliptic to polygonal. The raphe is generally straight, except for a median kink. The proximal raphe ends are expanded. Striae are slightly radiate, becoming parallel at the apices.

Mastogloia pumila

  1. Lateral sterna present
  2. Central partecta larger than distal partecta
  3. Striae uniseriate
  4. Raphe straight

Symmetrical biraphid - Valves are linear-lanceolate to elliptic-lanceolate with subtly protracted and broadly rounded apices, lateral sterna, and partecta of two different sizes. The striae are uniseriate and the raphe is straight, rather than sinuous.

Melosira dickiei

  1. Mantle narrow
  2. Ornamentation unorganized
  3. Internal valves present

Centric - Valves are cylindrical, with short mantles. Valves are finely punctate but lacking patterns of ornamentation. Cells produce a characteristic multi-walled endogenous resting spore.

Melosira normannii

  1. Cells large, with thick walls
  2. Rimoportulae present
  3. Central spiral pattern on valve face

Centric - Cells are large and heavily silicified. A small central area opens to spiral anastamosing rows of areolae. The mantle has pervalvar rows of areolae and a ring of rimoportulae. The internal margin of the mantle is polygonal.

Melosira undulata

  1. Cells large, cylindrical, and robust
  2. Striae conspicuous
  3. Mantle unevenly thickened
  4. Mantle rimoportulae evenly-spaced

Centric - Melosira undulata has large, robust, cylindrical frustules linked in long chains. Valves and mantles are conspicuously ornamented with rimoportulae and striae. A ring of evenly-spaced rimoportulae encircles the mantle near the valve/mantle interface. The mantle is unevenly thickened internally, giving an undulating appearance.

Melosira varians

  1. Cells cylindrical, forming filaments of linked cells
  2. Valve face and margin with little to no ornamentation

Centric - Cells cylindrical, often forming long chains. Valve face slightly convex, covered with very small spines. Unlike many Aulacoseira species, valves lack areolae.

Meridion alansmithii

  1. Valves elongate, linear-clavate
  2. Head pole attenuated
  3. Rimoportula present, near widest part of valve
  4. Sternum narrow, faint
  5. Costae present

Araphid - Valves are elongated and linear-clavate. The head pole is attenuated and subrostrate. A single rimoportula is located distal from the head pole, near the widest part of the valve. Costae mostly primary, with occasional secondary costa. The sternum is narrow and may be difficult to distinguish.

Meridion anceps

Diatoma anceps

  1. Valve symmetric to the transapical axis
  2. Ends subcapitate to capitate
  3. Costae 3.3-4.9 in 10 µm
  4. Central sternum present
  5. Distinct subapical rimoportula present

Araphid - Valves are symmetric and linear, with subcapitate to capitate ends. Costae measure 3.3-4.9 in 10 µm. Striae are visible in LM, but individual areolae are not resolved. The sternum is central and well-defined. Each valve has a single, sub-apical rimoportula.

Meridion circulare

  1. Valves linear-clavate
  2. Costae present
  3. Narrow sternum
  4. Single rimoportula

Araphid - Valves linear-clavate, asymmetric to the transapical axis. Costae are present running transversely across the valves. A narrow sternum extends the length of the valve. A single rimoportula is located near the headpole.

Meridion circulare var. constrictum

  1. Valves linear-clavate
  2. Headpole distinctly rostrate
  3. Costae present
  4. Sternum narrow
  5. Single rimoportula

Araphid - Valves are clavate, with a rostrate headpole. Costae extend transversely across the valve. A single rimoportula is present near the headpole. The sternum is narrow.

Meridion lineare

  1. Valves irregular in shape
  2. Forms ribbon-like colonies
  3. Costae perpendicular to apical axis
  4. Striae 16-18 in 10 µm

Araphid - Valves are isopolar, but slightly irregular in shape. Valves are linear-lanceolate, to oval in smaller specimens. Frustules typically attach to one another in long ribbon-like colonies. Transapical costae are mostly perpendicular to the apical axis and number 4-6 in 10 µm. Striae are distinct and number 16-18 in 10 µm.

Microcostatus krasskei

  1. Cells small
  2. Axial depressions present
  3. Sternum prominent

Symmetrical biraphid - Valves are small and lanceolate. Lyre-shaped depressions are present on each side of the central sternum. Striae are not visible in LM.

Muelleria agnellus

  1. Valve margins slightly convex
  2. Valves >9.5 µm wide
  3. Striae radiate, distinctly curved

Symmetrical biraphid - Valves are lanceolate, with slightly convex margins. Valves are wider than 9.5 µm. Striae are radiate, especially in the center of the valve, and distinctly curved. Proximal raphe ends are unilaterally deflected.

Muelleria gibbula

  1. Valves elliptic
  2. Valves <10 µm wide
  3. Striae radiate, straight

Symmetrical biraphid - Valves are elliptic and less than 10 µm wide. The central margin is often gibbous. Striae are radiate, especially in the center, and straight. Proximal raphe ends are unilaterally deflected. The central area is small.

Muelleria spauldingiae

  1. Valves elliptic, large
  2. Apices cuneate
  3. Striae straight

Symmetrical biraphid - Valves are large and elliptic with cuneate apices. Striae are radiate and straight. Proximal raphe ends are deflected unilaterally.

Muelleria tetonensis

  1. Valves linear-elliptic
  2. Valve margins parallel
  3. Striae radiate

Symmetrical biraphid - Valves are large and linear-elliptic, with parallel margins. Striae are radiate throughout. Proximal raphe ends are deflected unilaterally.