Cavinula vincentii

Valves are elliptic. Striae are 23-26 in 10 µm, and may be greater in some valves. Areolae are 28-33 in 10 μm. The axial area is narrow and linear, broadening slightly towards the central area; the central area is round to elliptic. The raphe is filiform with expanded central fissures. The terminal raphe fissures are small on the valve face. The striae are strongly radiate, and are usually visibly punctate. Long and short striae alternate in the central area. Short striae are present extending just inside the margin of the valve face, and continuing onto the mantle. The stria density increases towards the apices. Areolae are elliptic, with depressed occlusions, and with a row of elongated areolae along the axial area that lengthen to slit-like structures around the central area. At each apex one enlarged pore-like fissure is visible immediately adjacent to the distal fissures on the primary side of the valve; this pore is elliptical on the external surface and transapically elongated on the internal surface. Internally, the raphe is linear, terminating in a small helictoglossa at the terminal fissure. Helictoglossa not present at proximal fissure. Internally, the striae are positioned between costa thickenings, and each stria is covered internally by a hymen. Valves have two or more open copulae, with one row of pores.

Navicula pseudoscutiformis was identified from the Gulf of Finland (Snoeijs and Potapova, 1995, p. 32). The specimens are similar to C. vincentii in valve shape and features, however the specimens differ from C. vincentii by a lanceolate axial area and the absence of enlarged, pore-like structures at the apices. A specimen identified as N. pseudoscutiformis (Krammer and Lange-Bertalot,1986, fig. 59: 12) is also similar to C. vincentii, however it is difficult to discern the length of the areolae around the central area. Closer examination of specimens identified as C. pseudoscutiformis may reveal their affinity to C. vincentii.