Type:—"Fiesta Island, Mission Bay, San Diego, California, USA, April, 27, 2000", geographic coordinates 32°46’ N, 117°13’ W. Holotype BRM ZU 5/34, slide coordinates 15.6 E, 9.1 S. Isotypes in collection Sterrenburg #657 and collection Tiffany.

Valve (Figs 12, 13, 27, 28) with asymmetric crescent-shaped contour as in the genus Amphora, 70–90 μm long, 9–15 μm wide, with acute ends and a distinct unilateral stauros-like structure. Raphe situated almost at the periphery of the non-convex valve margin. Striae perpendicular, transverse circa 18–20 in 10 μm, longitudinal circa 20–23 in 10 μm. In SEM, the tegumental layer shows little surface relief (Figs 30, 32). External central raphe fissure endings very approximate and very slightly curved towards the convex half of the valve (Fig. 32). Basal layer: foramina transversely elongated oblong (Fig. 31), a transverse silica ridge (pseudo-stauros) is up to 3 interstriae wide (Fig. 31). The two layers of the sandwich valve are joined by longitudinal upright saepes with small perforations (Fig. 29, inset). The perforations are located underneath (in the figure!) the transverse bars of the basal layer.

Etymology:— The specific epithet refers to the type locality, Fiesta Island.

Habitat:— Muddy brackish to littoral marine sediment.

Distribution:— Type locality only, not rare in the sample, but see Observations.

Observations:— Detached valves of Haslea feriarum would be labeled as an Amphora in routine LM studies and in fact this may have been done. For instance, the reference to Amphora laevis Gregory in Hendey (1964:267) contains data similar to those of our species. The differences between these two entities are evident, however. The multiple girdle bands of A. laevis clearly illustrated in Gregory (1857: Pl XII, Fig. 74) are typical of Amphora but are not seen in any Haslea species. On the other hand, the sandwich structure of the valve of H. feriarum is typical of Haslea but excludes Amphora. Specimens matching H. feriarum (but only observed in LM!) have been found (FASS) in samples from New Zealand (Leg. Lesley Rhodes) and the Wadden Sea (The Netherlands) but their morphology has not yet been examined in SEM.