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 Mastogloia ovata Grunow Figs 65, 66 Ref. illus.: Hustedt 1931 –1959, p. 476, fig. 895 Lobban et al. 2012 , p. 281, pl. 35, figs 1, 2 (as “ M. pseudolatecostata ”) Lobban et al. 2012 , p. 279, pl. 33, figs 7, 8 (as “ M. ovata ”) Samples: GU44T-1, GU44 AJ , GU44AU-1; GU52P-7; GU70A-2A Our specimen published as voucher for M. pseudolatecostata must be rejected because the stria density is too high (21–24 vs 12–14 in 10 µm). It is a better match for M. ovata than the voucher specimen cited in the same paper. SEM images of such specimens are shown in Figs 65, 66. A specimen from Bikar Atoll, Marshall Islands that matches M. pseudolatecostata is shown in Fig 67 ; this species not yet identified in Guam . The specimen claimed as a voucher for M. ovata in Lobban et al. 2012 less clearly matches the description in Hustedt (1931 –1959) and close to Hein et al. (2008 , pl. 40, fig. 3) “ Mastogloia cf. ovata . ” Comments: The inner margin of M. ovata has indentations at each cross wall ( Fig. 66 ), that of M. pseudolatecostata in the middle of each partectum ( Fig. 67 ).