During a survey of the diatom flora of Longemer Lake (Xonrupt-Longemer, Vosges, France), two species with an unusual biogeographical distribution were observed. Psammothidium abundans, previously considered being a sub-Antarctic endemic but today also found in rivers in Sweden, Ireland and the UK, and Achnanthidium sublineare, up to now confined to northern Europe, were identified. These are the first records of these rare diatom species in France (A. sublineare) and in a European lake (P. abundans). Since there are only a few illustrations of these two species in the literature, both populations are illustrated using light and scanning electron microscopy in order to provide a detailed morphological account. Details on their actual biogeographical distribution are added.

在对Longemer湖（法国Vosges的Xonrupt-Longemer）的硅藻群落进行的调查中，观察到两种生物地理分布异常的物种。Psammothidium量丰度，以前被认为是一个次南极特有但是今天在瑞典，爱尔兰和英国，和河流也发现Achnanthidium sublineare，到现在为止仅限于北欧，进行鉴定。这些是这些稀有硅藻物种在法国（A. sublineare）和欧洲湖泊（P. abundans）中的第一个记录。）。由于文献中仅对这两种物种进行了少量说明，因此使用光镜和扫描电子显微镜对这两种种群进行了说明，以提供详细的形态学说明。添加了有关其实际生物地理分布的详细信息。