H. avium Tiffany, Herwig & Sterrenburg, sp. nov. (Figs 19, 20: LM. 58–64: SEM) Type:— " Birdrock, La Jolla, California, USA, January, 17, 2003, from Codium", geographic coordinates 32°48’N, 117°16’ W. Holotype BRM ZU9 /90, slide coordinates holotype: 4,4 E; 3,4 S, isotype: 4,8 E; 5,3. Isotypes also in collection Sterrenburg # 728. Valve (Figs 19, 20) robust, lanceolate, 38–45 μm long, 6–9 μm wide, with acute apices. Striae transverse slightly radiate, circa 13–15, longitudinal much finer, circa 30 in 10 μm. A few central transverse striae somewhat more radiate and slightly shortened, leaving a tiny more or less oval central area, but this is variable (Figs 19, 59, 64). Axial area extremely narrow, inconspicuous in LM. In SEM, the tegumental layer, with longitudinal fissures that are continuous over most of the valve but sometimes interrupted near the central area, may show marked surface relief (Figs 60, 62, but not in Fig. 63). External raphe fissures often undulating in the middle (Fig. 62, less so in Fig. 63), central endings tightly curving hooks that form depressed pits with tooth-like projections (Figs 62, 63), external terminal endings deeply depressed and retrograde (Fig. 60). Internally, no central bars apparent, one side of the raphe ridge thickened but no pronounced accessory silica ridge paralleling the raphe ridge present (Figs 59, 64). The entire internal raphe ridge, including the central raphe node, tilted sideways (Fig. 64). Basal layer: foramina longitudinally elongated oblong, transverse bars of the grate considerably broader than the longitudinal (Fig. 64). Etymology:— The specific epithet (genitive, plural of Latin “avis” = bird) refers to the birds of the type locality. Habitat:— Littoral marine, epiphytic and in sediment. Distribution:— Known from the type locality only, not rare, also in several other samples from the Birdrock locality in collections Tiffany and Sterrenburg. Observations:— This species somewhat resembles H. tsukamotoi and H. meteorou with regard to the marked surface relief of the robust valve, the hook-shaped external central raphe endings with tooth-like projections and the sideways tilted internal central raphe node, but the external central raphe endings and tooth-like projections are very different in shape. Also, the basal layer and striation are clearly different. Saepes not satisfactorily visualized, no fragmented valves found. In LM, this species may be readily mistaken for one of the Naviculae sensu stricto (the “ Lineolatae”) but the SEM images are decisive. In Fig. 63 the coarse transverse bars of the basal layer grate “shine through” the tegumental layer as ghost images, permitting a transverse stria count in the SEM material. Without this, it would not have been possible to verify that the exterior views of Figs 58, 60 and 62 and the interior views of Figs 59, 61 and 64 are indeed of the same species. In H. avium the longitudinal striae are much finer than the transverse, which excludes a match with H. britannica, H. howeana or H. nautica.

Published as part of Sterrenburg, Frithjof A. S., Tiffany, Mary Ann, Hinz, Friedel, Herwig, Wulf E. & Hargraves, Paul E., 2015, Seven new species expand the morphological spectrum of Haslea. A comparison with Gyrosigma and Pleurosigma (Bacillariophyta), pp. 143-162 in Phytotaxa 207 (2) on page 155, DOI: 10.11646/phytotaxa.207.2.1, http://zenodo.org/record/13637746