Pteroncola marina Holmes & Croll

Lobban, Christopher S., 2015, Benthic marine diatom flora of Guam: new records, redescription of Psammodictyon pustulatum n. comb., n. stat., and three new species (Colliculoamphora gabgabensis, Lauderia excentrica, and Rhoiconeis pagoensis), Micronesica 2015 (2), pp. 1-49 : 13

Pteroncola marina Holmes & Croll Figs 129, 130

FRAGILARIALES Silva : Fragilariaceae Greville

Ref. illus.: Holmes & Croll 1984, figs 2–15; Round et al. 1990, pp. 390–391, figs a–i

Samples: GU41D-A1; Jordan plankton tow Talofofo; black mangrove roots at Merizo (coll. Shiori Tamura)

Dimensions: Length 5.3–8.4 µm, width 2.6 µm; striae 75 in 10 µm

Diagnostics: Small tabulate frustules; exceedingly fine striae consist of very closely spaced pores (smaller than the apical pores); apical pores aligned conspicuously at 90° to the striae, as seen in girdle view. Thickened spots along edge of valve mantle.

Comments: The striae are alveolate, opening internally by single pores ( Round et al. 1990), as in Caloneis and Oestrupia ; Fig. 130 is consistent with this, and the pores can be seen through the external areolae. Round et al. (1990) proposed synonymy of P. marina and P. inane (Giffen) F.E. Round ( Dimerogramma inane Giffen 1970a , figs 20–22), which has elevated apices, but reexamination of Giffen’s materials in LM and SEM (A. Witkowski, personal communication) showed that P. marina is distinct. Almandoz et al. (2014) described a new species, P. carlinii Almandoz & Ferrario with much different striae, and also emended the genus description.