Marine benthic diatoms of Guam: new records, Dictyoneis apapae sp. nov., and updates to the checklist Author Lobban, Christopher S. Division of Natural Sciences, University of Guam, Mangilao, GU 96923, USA clobban @ triton. uog. edu clobban@triton.uog.edu Author Witkowski, Andrzej University of Szczecin, Institute of Marine and Environmental Sciences Mickiewicza 16 a, PL 70 - 383 Szczecin, Poland text Micronesica 2023 2024-06-06 2023 2 1 75 journal article 299061 10.5281/zenodo.12118784 2b921c3c-8618-439e-96da-1de9c66a90f9 0026-279X 12118784 “ Bacillaria Group B” sensu Schmid var. tumidula Figs 10–14 Previous Micronesian record: J.S. Park et al. 2022 , p. 45, figs 144, 145 Samples: GU21AM-2, GU21AN-1; GU52J-3, GU52K-4, GU52S-2; GU58G-4D Diagnostics: Colonial, as in B. paxillifera , the “slide rule” diatom, but inflated in the middle. Uniseriate striae with external costae. Comment: As noted by Lobban et al. (2012) for the nominate form, marine forms were orphaned when Jahn & Schmid (2007) redefined B. paxillifera as freshwater/brackish, naming several new species, but excluding three marine groups distinguished by Schmid (2007) . Our assignment of this variety to Group B, based on the nominate form, has not been verified and remains in limbo until Jahn completes her analysis. The short cristae at the central area are characteristic but we have images of specimens without them and without costae; further progress awaits completion of work on this group.