Mastogloia obliqua Hagelstein, 1939

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 : 7-8

Mastogloia obliqua Hagelstein Figs 62, 63

Ref. illus.: Hagelstein 1939, pl. 5, figs 12, 13; Giffen 1980, pl. 2, figs 23, 23a, 24; Loir & Novarino 2013, pl. 16c

Samples: GU66F-4

Dimensions: Length 13 µm, width 4.4 µm, striae ca. 25 in 10 µm.

Diagnostics: Small, rostrate valves with one partectum on each side (sometimes two, as shown by Hagelstein 1939), placed slightly obliquely across the central area.

Comments: Comparable with M. tenuis Hustedt ( Lobban et al. 2012, pl. 37, figs 6–8), which is not rostrate, has finer striae, and has two small tapering partecta bordering the larger partecta on each side, the chambers symmetrically placed (as in most Mastogloia spp. ) and also has axial costae bordering the internal raphe-sternum. Also similar to M. giekesii Cholnoky ( Loir & Novarino 2013, pl. 13a), which is rostrate, has two chambers on each side (apparently never only one), symmetrically placed.

Figures

Figures 51–70. Figs. 51–55. Mastogloia emarginata. Figs 51-54. LM views of two specimens focused on valve face and valvocopula, arrowhead indicates one of the prominent exit pores of the partecta (GU44AR-2) (DIC). Fig. 55. Internal view of valve and valvocopula (GU55B-4) (SEM). Figs 56, 57. Mastogloia ovulum specimen at two focal planes (GU44K-6) (DIC). Figs 58-61. Mastogloia matthaei, two specimens at two focal planes (GU52P-2) (DIC). Figs. 62, 63. Mastogloia obliqua, valve at two focal planes (GU66F-4) (DIC). Figs. 64–67. Mastogloia peracuta (GU44AP-9). Figs 64, 65. Specimen at two focal planes (DIC). Figs 65, 66, External views of two specimens in SEM. Figs 68–71. Mastogloia pumila. Figs 68, 69. Specimen in DIC at two focal planes (GU52P-1; catalog # GUD002950). Fig. 70. Internal aspect of valve and valvocopula (GU52P-9) (SEM). Fig. 71. Frustule showing both internal and external valve faces. Scale bars: Figs 51–69 = 5 µm, Figs 70, 71 = 3 µm.