Phylum: Bacillariophyta  Family: Gomphonemataceae

Encyonema silesiacum (Bleisch) D.G. Mann

A common species in flowing water

References: 
Round, F.E., Crawford, R.M. & Mann, D.G. (1990) The Diatoms: Biology and Morphology of the Genera
Kelly, M. (2000) Identification of Common Benthic Diatoms in Rivers