We investigated the taxonomic classif i c ations of three of diatoms growing in inorganic, strongly acidic waters in Japan, and obtained the following results. The undulation of both margins of Pinnularia braunii var. undulata is observed in large individuals only, whereas in small individuals both margins are often swollen and resembles Pinnularia braunii in shape, though the valve breadth of P. braunii is narrower and consequently the status of P. braunii var. undulata should be changed.
The next taxon we investigated is often found growing together with P. braunii. The valve shape closely resembles that of P. braunii, but the valve breadth of this taxon is 4.5-6 mm, against 7.3-8.5 for P. braunii. Since the breadth is clearly smaller, it would seem appropriate to treat this as a new taxon, P. gracilivalvis.
We try to compare the photos of the lectotypes taxon, P. acoricola with specimens with equal valve length which is treated as P. acoricola by many Japanese researcher. the breadth is smaller in all Japanese specimens. Moreover, the valve shape of most of them is elliptical, whereas that in most P. acoricola is lanceolate. For these reasons, we suggest the diatom considered to be P. acoricola in Japan is accepted as a new taxon, P. osoresanensis.

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Epilithic algae were collected at the outflow of the Suzumeno-yu at Isobe Hot Springs, Gunma Prefecture in June,2000; at the time of sampling, the water temperature was 31C, the pH was 7.6 and the concentration of NaCl was 0.49%. Almost 100% of the co llected algae belonged to the taxon in this study. The valves of these specimens were elliptical to linear-lanceolate, and the ends were acute or rostrate. The valve length was 9-24 (30) μm, breadth was 3-5 μm and there were 13-18 striae in 10 μm. The striae were perpendicular to the raphe or weakly radiate from the valve center. This taxon resembles several taxa in Navicula (e. g. N. aquaedurae, N. arcotenelloides, and N. caterva), but appears to be a new taxon due to differences in valve form. Since we believed this species to be identical to the species recorded as Navicula sp. at Mine Hot Springs by Tanaka and Nakajima (1985), we propose the new name Navicula tanakae Fukush., Ts. Kobay. &Yoshit. nov. sp. in honor of Hiroyuki Tanaka, at first author of that study.

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The freshwater diatom flora of the Hii River in Western Japan is studied. In December 1999,27 samples examined were collected from cobbles, pebbles and sands at ten sampling stations situated at almost regular intervals along the main course of Hii River. In total 180 diatom taxa belonging 58 genera were identified, and were illustrated together with 20 unidentified ones. Encyonema incurvatum Krammer was separated from Encyonema silesiacum (Breisch) D. G. Mann by the relationship between length and width, in addition to the density of areolae. Gomphonema tetrastigmatum Horikawa et Okuno, Ceratoneis arcus var. hattoriana F. Meister and Navicula aequatorialis Heiden are respectively transferred taxonomically suitable genera as follows: Gomphoneis tatrastigmata comb. nov., Hannaea arcus var. hattoriana comb. nov. and Luticola aequatorialis comb. nov. Because the type of Navicula exigua (W. Greg. ) Grunow has not been confirmed, N. exigua var. elliptica Hust. and N. exigua fo. undulata Hust. are raised to independent species, with transfer to the genus Placoneis Mereschk., i. e. Placoneis elliptica comb. nov. et stat. nov. and Placoneis paraundulata nom. nov.

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Lake Takahoko in Aomori Prefecture is known to be a brackish-water lake leading to the Pacific Ocean by a narrow waterway. Diatom thanatocenoses from surficial sediments and water properties such as temperature, DO, salinity, conductivity, turbidity and pH were investigated.
The results are as follows:
(1) Most of the lake water is mesohaline, although oligohaline water exists partially in the innermost part of the lake.
(2) Bottom sediments, from deeper than 2m water depth, are composed of black surficial oozes smelling strongly of H₂S.
(3) A total 137 taxa, belonging to 40 genera and comprising 128 species and 9 varieties, were found in the surficial sediments. Diatom assemblages are composed of fresh and fresh-brackish water species (46.3-83.5%), brackish water species (6.5-25.0%), and marine and marine-brackish water species (10.0-36.0%).

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Shiozawa mineral spring is situated in the northwestern part of Nagano City, Nagano Prefecture. The author studied the diatom flora of this spring from March 1953 to March 1954. Shiozawa mineral spring is a salt water spring containing 885-893 mg/l Cl- with a water temperature of 14.0-23.4°C, and a pH of 6.8-7.0. Diatom species consisted of 7 taxa, two of which, Navicula erifuga Lange-Bert. and Surirella ovalis Bréb., were salt tolerant. Navicula erifuga was the dominant species. The morphological characteristics of Navicula erifuga were observed. The valve length and breadth of 50 living cells were measured monthly within the previous recorded ranges, and no seasonal change was noted. In this mineral spring, elliptic-lanceolated valves of N. erifuga were the commonest, and their edges were often cuneate and subrostrate. They slightly out-numbered the other shapes. Some noted differences were seen in the shape of the central area and the number of striae that converge on the area between the central pores. The central area of most observed valves is rectangular on the primary side and lanceolate on the secondary side (71%). About 25% of the observed valves are lanceolate on both sides. Less than 5% of the observed valves are rectangular on both sides. About 40% of the valves that have a rectangular shape on the primary side and lanceolate shape on the secondary side or a lanceolate shape on both sides have three striae on both sides; and 90% of the valves that have a rectangular shape on sides have three striae on the primary side and two striae on the secondary side. These individuals are dominant in each group. Striae number was 12-14 in 10μm.

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Epilithic diatoms were collected on F e bruary 23 and 24,2002 from two spas,1t45S pa and Yugawara Spa, located in central part of Japan. A total of 20 samples were collected, of which 12 contained diatoms. At sampling sites where diatoms were found, the water temperature ranged from 18-45t, the pH was 6.7-8.7 and the concentration of NaC1 was 0.05-0.16%. A total of 17 diatom taxa were observed. The commonest taxon was Pinnularia joculata which is regarded as a tropical species, followed by Nitzschia amphibia, Achnanthes minutissima, Navicula veneta and Nitzschia microcephala which were considered to be alkalifilous taxa. Dominant taxa were almost the same as the common taxa, though the order was slightly different. Of the 16 identified taxa, only 9 were salt tolerant with a relative frequency of 56.3%, which is reasonable value under low NaCl concentration (0.05-0.16%).

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New names for 20 taxa are described here based on our detailed observations, which will be published as parts of our atlas (in preparation). Many of them were prepared by Prof. Dr. Hiromu Kobayasi in his lifetime.

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