All Taxa

Catenulaceae: Amphora

Cells solitary, moderately or strongly dorsiventral, semi-elliptical, semi-lanceolate or semi-linear in valve view, with bluntly rounded to rostrate ends. In girdle view frustules are elliptical to almost rectangular with broadly rounded to truncate ends. Valve mantle deeper on dorsal margin than on ventral margin, marginal ridge often present at junction of valve face and dorsal margin.

Striae uniseriate, with round, elliptical or transapically elongate areolae, sometimes complex and chambered (loculate); often interrupted by a transapical plain (‘hyaline’) area at the centre (fascia) and/or by straight or curved longitudinal plain strips; dorsal striae usually radial or parallel throughout; ventral striae short, usually radial towards the centre but convergent towards the poles.

Axial area narrow to broad. Central area often expanded and sometimes forming a broad transapical band (fascia), often differently developed on the ventral and dorsal sides of the valve; or, there may be an independent plain area on the dorsal side, separated from the central area by a few areolae.

Raphe eccentric, closer to the ventral margin and often appearing to be positioned on a raised ledge; straight, or slightly or strongly arched towards the dorsal side; external central raphe endings straight or curved or bent towards the dorsal side; internal central endings straight, often ending in and linked by a small ridge; terminal fissures bent towards the dorsal side.

Bands open, plain or porous, several per theca (but usually less than in Halamphora) much wider on the dorsal side than on the ventral side. One complex chloroplast per cell, with its apically constricted centre lying against the ventral side of the girdle, from which several lobes extend across beneath the valves to the dorsal side of the girdle.

Solitary, free-living or attached via the ventral side.