STUDIES ON THE FRESHWATER CENTRICAE OF CHINA

1. Melosira roeseana var. xizangensis Chen, var. nov. (Figs. 1, 2)Differt a typo valvis in area striata sparsim denticulatis, ad marginem cum denti culis longioribus, erassioribus, subcurvatis et dense ordinatis, 6—9 in 10 μ.Cellulis 29—70μ diam., 10—28μ altis; striis ad sulcum 12—19 in 10μ, ad pseudo- sulcum 10—15 in 10μ.Hab. in scopulis humidis ad fontem montanum(alt. 2700 m) ad Nyalam Xian in Xizang (Tibet). Typus: TB75028 2. Cyclotella hubeiana Chen et Zhu, sp. now (Figs. 3, 4)Frustula tympaniformia, in catenem brevem conjuncta; valvis superficie concen trice undulatis, 6.5—33μ diam.; margine 2/3—3/4 diametri lato, striis crassis, aliquan tum irregulariter undulatis, alternatim longioribus et brevioribus, 10—14 in 10μ; prope marginem striis umbrosis (i.e. processis tubulatis in surperfaciem interiorem valvae) inter stras instructis, 3—6 in 10μ; area centrali circulari, laevi vel sparsim punctata.Hab. In fluvum ad Zaoyang Xian in Hubei Sheng (Typus); In lacum artifactum ad Yidu Xian in Hubei Sheng (Paratypus).Typus: HP76501Paratypus: HP76904 3. Cyclotella curvistriata Chen et Zhu, sp. nov. (Fig. 5) Frustula disciformia; valvis planis, 9.5—16μ, diam.; margine lato, juxta quoque medio laterum areae centralis macula ampla elliptica vel rotundata et leviter elevata instructo, striis versus quoque maculum regulariter curvatis, (12—) 16—20 in 10μ; area centrali triangulari, raro tetrangulari, angulis rotundatis, lateribus valde retusis, intro quoque angulo cum macula ampla elliptica vel rotandata, in parte cetero sparsim punctata.Hab. In fluvum ad saxa in torrentes (alt. 2960 m) ad Xiangcheng Xian in Sichuan Sheng fypus: HD85 4. Cyclotella rhomboideo-elliptica Skuja, Char, emend. Chen et Zhu (Fig. 6) Valvis rhomboideo-ellipticis, 10—54μ longis, 8—44 μ latis; striis punctatis ad marginem duobus, versus aream centralem unicis, (8—) 10—12 (—14) in 10 μ; ad marginem striis umbrosis oblongis geminatis instruetis, (4—) 5—6 in 10 μ; area centrali arcuatavel subtruncto-convexa, hyalina et sparsim aut plus miimsve radiatim punctata, ad marginem processo tuibalato bnevi ornata, illo epithecae et hypothecae oppositim sita.Hab. in lacibus "Dianchi" (ad Kunming Shi), "Yangzhonghai" (juxta Yiliang Xian), " Fuxianhu" (juxta Cheng-jiang Xian) et "Xingyunhu" (juxta Jiangchuan Xian) in Yunnan. Topotypus in YN1082 and 1083 (Dianchi); YN188, 696 and 697 (Yangzhonghai); YN677 and 678 (Fuxianhu); YN516—518 and 521 (Xingyunhu).