Genus: Pseudostome lacks lobed collar; test round or oval in cross-section; pseudostome relatively large, with or lacking a collar (Illustrated Guide, 1985).
Species: Test pyriform, flask-shaped, or ovoid; neck variable in length; aperture terminal, typically circular; test composed of angular sand-grains, diatoms; 60-580 μm by 40-240 μm (Kudo, 1966).

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Test slightly curved, posteriorly rounded
D. oblonga 370 x 180 μm L/W=2.1 P/W=0.39 Kamonoyachi n. Zao onsen Yamagata, 2005	D. oblonga 250 x 80 μm L/W=3.1 P/W=0.48 Koigakubo marsh Tessei-cho Okayama, 2004	D. oblonga 225 x 90 μm L/W= P/W= Ikenokochi m.2 Tsuruga Fukui, 2006	D. oblonga 165 x 75 μm L/W=2.2 P/W=0.33 Akigase Park Saitama city Saitama, 2005
D. oblonga 158 x 75 μm L/W=2.1 P/W=0.40 Numa-no-hara m. Madarao highland Niigata, 2005	D. oblonga 157 x 64 μm L/W=2.5 P/W=0.39 Yamaguchi Univ. Yamaguchi, 2004	D. oblonga 116 x 43 μm L/W=2.7 P/W=0.40 Uruguay, 1999	D. oblonga 119 x 44 μm L/W=2.7 P/W=0.45 Asaka Saitama, 1998
Test slightly constricted anteriorly
Test L/W less than 2.0
D. oblonga 240 x 140 μm L/W=1.7 P/W=0.52 Sashi-ohgi Saitama, 2002	D. oblonga 225 x 125 μm L/W=1.8 P/W=0.60 Abiko Chiba, 2000	D. oblonga 90 x 55 μm L/W=1.6 P/W=0.60 Iroha-numa Zao mountain Yamagata, 2005
Test L/W more than 2.0
D. oblonga 200 x 95 μm 195 x 85 μm L/W=2.1,2.3 P/W=0.35.0.36 Shibu-ike Shiga highland Nagano, 2005	D. oblonga 143 x 77 μm L/W=1.9 P/W= Maeyama marsh Shiga highland Nagano, 2007	D. oblonga 180 x 90 μm L/W=2.0 P/W=0.31 Ushidome-ike Norikura highland Nagano, 2005	D. oblonga 160 x 80 μm L/W=2.0 P/W=0.38 Kisuge konuma Shimogo Fukushima, 2005
D. oblonga 150 x 80 μm L/W=1.9 P/W=0.38 Furuike marsh Togakushi highland Nagano, 2005	D. oblonga 135-150 x 55-67 μm L/W=2.2-2.5 P/W=0.37-0.40 Tanohara marsh Shiga highland Nagano, 2004	D. oblonga 110-145 x 51-74 μm P/W=0.33-0.43 Tanohara marsh Shiga highland Nagano, 2006	D. oblonga 135 x 70 μm L/W=1.9 Tanohara marsh Shiga highland Nagano, 2007
D. oblonga 145 x v μm P/W= Midagahara 5 Tate-yama Toyama, 2006	D. oblonga 170 x 70 μm L/W= P/W= Kamino-tanbo Tsugaike highland Nagano, 2006	D. oblonga 120 x 55 μm L/W=2.2 P/W=0.36 Watasuge marsh Tsugaike highland Nagano, 2005	D. oblonga 140 x 56 μm L/W= P/W= Yokotashiro 1 Katashina Gunma, 2007
D. oblonga μm L/W= P/W= Fujimitashiro Katashina Gunma, 2007	D. oblonga μm L/W= P/W= Hachimantai Mt. Hachimantai Iwate, 2007	D. oblonga μm L/W= P/W= Sensho-ga-hara Shizukuishi Iwate, 2007	D. oblonga 113 x 55 μm L/W=2.1 P/W=0.44 Hakama marsh Madarao highland Niigata, 2005
D. oblonga 110 x 50 μm L/W=2.2 P/W=0.44 Komado marsh Showa and Tajima Fukushima, 2004	D. oblonga 110 x 55 μm L/W=2.0 P/W= Komado marsh Showa and Tajima Fukushima, 2007	D. oblonga 170 μm L/W= P/W= Japan, 199?	D. oblonga or D. pyriformis ? 68 x 40 μm L/W=1.7 P/W=0.40 Higashi-hirosima Hiroshima, 1998
Test laterally straight
Pseudostome/Test width (P/W) more than 0.5
D. oblonga 210 x 80 μm L/W=2.6 P/W=0.50 Tanohara marsh Shiga highland Nagano, 2005	D. oblonga 185 x 80 μm L/W=2.3 P/W=0.56 Japan, 199?	v. venusta 170 x 60 μm L/W=2.8 P/W=0.50 Kitamoto nature o.p. Kitamoto Saitama, 2005
Pseudostome/Test width (P/W) less than 0.5
D. oblonga 185 x 65 μm L/W=2.8 P/W=0.43 Ushidome-ike Norikura Nagano, 2005	D. oblonga 185 x 85 μm L/W=2.2 P/W=0.39 Kodanuki marsh Fujinomiya Shizuoka, 2005	D. oblonga 145 x 55 μm L/W=2.6 P/W=0.42 Hikage marsh Shiga highland Nagano, 2005	D. oblonga 143 x 65 μm 140 x 70 μm L/W=2.6 P/W=0.40,0.43 Mida-ga-hara Gassan Yamagata, 2005
D. oblonga ? 280 x 140 μm L/W=2.0 P/W=0.36 Imori pond Myoko highland Niigata, 2004	D. oblonga 140 x 60 μm L/W=2.3 P/W=0.42 Hakkoda Gourd line Hakkoda mountain Aomori, 2005	D. oblonga 130 x 65 μm L/W=2.0 P/W=0.38 Nidanuma Tsuchiyu-onsen Fukushima, 2005
D. oblonga 127 x 60 μm L/W=2.1 P/W=0.42 Kamonoyachi n. Zao onsen Yamagata, 2005	D. oblonga 120 x 60 μm L/W=2.0 P/W=0.42 Nidanuma Tsuchiyu-onsen Fukushima, 2005	D. oblonga 110 x 65? μm L/W=1.7 P/W=0.35 Hikage marsh Shiga highland Nagano, 2005	D. oblonga 105 x 50 μm L/W=2.1 P/W=0.50 Kannon-numa Shimogo Fukushima, 2005
D. oblonga 105 x 40 μm L/W=2.6 P/W= Jionji-shinsui p. Iwatsuki-ku Saitama, 2006	D. oblonga μm L/W= P/W= Hachiman-numa m. Hachimantai Iwate, 2007	D. oblonga ? 137 x 58 μm L/W=2.4 P/W= Akebono marsh Tsuchiyu-onsen Fukushima, 2005
Misc.
D. oblonga or D. pyriformis ? 94 x 60 μm L/W=1.6 P/W=0.42 Ushidome-ike Norikura highland Nagano, 2005	D. oblonga or D. pyriformis ? 104 x 70 μm L/W=1.5 P/W=0.34 Kodanuki marsh Fujinomiya Shizuoka, 2006	D. oblonga or D. pyriformis ? 185 x 115 μm L/W=1.6 P/W= near Omine mt. Minakami Gunma, 2006	D. oblonga ? 40 x 21 μm L/W=1.9 P/W=0.62 Kabuto-yama Nishi-no-miya Hyogo, 2004

Similar species -->> D. pyriformis;
Similar Genus -->> Pseudodifflugia; Diaphoropodon

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