The genus Kobayasiella includes species difficult or even impossible to identify in LM. Only EM allows observation of the ultrastructural features helping in diagnostic species circumscription. Recent surveys of the epilithic diatoms in the running waters of Reunion Island led to the discovery of a new species, K. bebourensis. This species differs from all previously described ones by the uniseriate striae composed of areolae occluded by a cribrum. Besides, two other species, the so rarely recorded K. jaagii (F. Meister) Lange-Bert. and K. micropunctata (H. Germ.) Lange-Bert., were collected in two alpine lakes of the French Pyrenees. K. jaagii lacks an umbilicus in the raphe, which is considered one of the most important diagnostic criterions of the genus. However, this species shows a combination of characteristics including it within the genus Kobayasiella. K. micropunctata is a typical representative of the genus Kobayasiella matching all the ultrastructural features of the genus. K. bebourensis and K. micropunctata have a cingulum composed of at least three connecting bands.