We present three new species, Diploneis implicatus, Diploneis lacustris and Diploneis pumicosus, from the littoral zone of Lake Baikal. Descriptions of these species are based on light and scanning electron microscopical features that distinguish them from other taxa. Diploneis implicatus exhibits external openings of each stria areola flanked by short siliceous thickenings of the vimenes and virgae forming a regular pattern on the external valve that is unique for the genus. Similar structures have previously been reported only in the distantly related and ecologically different Craticula citroides. Diploneis lacustris possesses a conopeum, uncommon in Diploneis and known only in Diploneis aokiensis from Japan. In our species, the conopeum is variable in structure and only developed in the apical quarter of the valve. The third species, Diploneis pumicosus, has a distinctive raphe system morphology similar to that in the single valve of Diploneis conopeospongiosa from Lake Baikal. All three species inhabit silty bottom habitats at depth of 20 m or more, and have so far been found in the southern basin of Lake Baikal. The diversity of Diploneis species in Lake Baikal is a rich resource for further understanding the genus.

中文翻译：

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贝加尔湖双生硅藻(Bacillariophyta) 三个新种

我们展示了来自贝加尔湖沿岸地区的三个新物种 Diploneis implicatus、Diploneis lacustris 和 Diploneis pumicosus。这些物种的描述基于将它们与其他分类群区分开来的光和扫描电子显微特征。Diploneis implicatus 表现出每个乳晕纹的外部开口，两侧是 vimenes 和 virgae 的短硅质增厚，在外部瓣膜上形成该属独有的规则图案。以前仅在远亲和生态不同的 Cticula citroides 中报道过类似的结构。Diploneis lacustris 拥有一个 conopeum，在 Diploneis 中不常见，仅在日本的 Diploneis aokiensis 中已知。在我们的物种中，锥体的结构是可变的，仅在瓣膜的顶端四分之一处发育。第三种，Diploneis pumicosus，具有独特的中缝系统形态，类似于来自贝加尔湖的 Diploneis conopeospongosa 的单瓣。这三个物种都栖息在 20 m 或更深的粉质底部栖息地，迄今为止已在贝加尔湖南部盆地发现。贝加尔湖 Diploneis 物种的多样性是进一步了解该属的丰富资源。