Surirella lacrimula J.D. English 2012 (LM: Figs 55–66, SEM: Figs 67–77, 105)

Observations:— LM: Valve outline ovate with broadly rounded headpole and cuneate footpole (Figs 55–66). Valve dimensions (n = 30): length 24–34 μm, width 10.3–13.1 μm (measured at the widest part of the valve), length/width ratio 2.1–2.6. Valve composed of two distinct portions: central portion and outside portion (indicated in Fig. 59). Fibulae evident, spanning c. 1/4 of valve width, not extending to midline, 7–9 in 10 μm. Fibulae parallel at valve middle, radiate approaching apices.

SEM: Valve face flat making CSBs difficult to distinguish as CSBs not elevated from OFCs (Fig. 67–71). Striae multiseriate, composed of 3 or 4 rows of areolae, 30–32 in 10 μm (measured from SEM images, n = 4). Outside openings of areolae slit-like (Figs 68–71). Raphe canal located directly on mantle. Internally, valve composed of two portions: central portion and outside portion (indicated in Fig. 74). Wall of raphe canal growing slightly into cell cavity so that the portulae are easily visible (Figs 72–74). Fibulae short, a few bifurcate, spanning c. 1/4 of valve width, not extending to valve midline (Figs 72–74). Raphe continuous at headpole (Fig. 76, wavy arrow), but interrupted at footpole (Fig. 77, two arrows). One to three portulae occurring between two adjacent fibulae (Fig. 75, three arrows; Fig. 105, three arrows).

Distribution:— S. lacrimula was found in the same site with S. liubingii . From the literature, this species appears to have a global distribution as it has been reported in the USA, France, Argentina, and Iran (English & Potapova 2012, Bey & Ector 2013, Seeligmann & Maidana 2019, Safiallah et al. 2020).