angulata has a more oval hood, the lateral carinae shorter and with one row of areolae in the highest part and the paranota narrower with the humeri less projected (Figs.
We observed that the subcostal area is narrower in males (three rows of areolae in the widest part--Fig.
Paranota with outer row of areolae larger than the ones in the inner row, or paranota with only one row of areolae 2
Paranota with at least two rows of areolae, these subequal in size 5
with 4-6 long setae, posterior areolae
with 1 long seta.
5, 11-12 dorsal striae in 10[micro]m, 12-13 ventral striae in 10[micro]m, 18-20 striae in 10[micro]m at the ends, 36-38 areolae in 10[micro]m.
Nevertheless, the fine valve morphology of our specimens clearly differs from all the above mentioned in the absence of transapical costae and in the structure of the central striae with some areolae smaller and partially occluded.
Striae uniseriated, slightly radiate all along the valve, sometimes parallel or convergent at the ends, areolae apically elongated, to the apices the areolae are more rounded or even transapically elongated.
5-4, 10-12 dorsal striae in 10[micro]m, 12-14 ventral striae in 10[micro]m, 16-20 striae in 10[micro]m at the apices, 35-38 areolae in 10[micro]m.
Striae parallel to slightly radiate, irregular in length; areolae difficult to see even with SEM.
Raphe-less valve: striae composed of 2-4 (5) areolae separated by longitudinal hyaline lines.
Valve face with two differentiated areas, the central one tangentially undulated, with irregular areolae that do not penetrate the siliceous wall and the external one with areolae arranged in multiseriate fascicles and internal chambers.
Uniseriate striae, radiate, composed of few transapically elongated to circular areolae.
Scutum dull, smooth, granulated, with a few areolae near the posterior margin.
The above species can be recognized by the different sculpture (scutum granulated, with a few small areolae near the posterior margin in D.