Phylum: Ochrophyta   Family: Tabellariaceae

Oxyneis binalis  (Ehrenberg) Round

It seems to be a rarely recorded diatom of oligotrophic acid water; it is not well known and does not feature in many texts. It is most often seen in a 'girdle view' as chains of frustules (not zig-zag) resembling other genera very closely. The individual valves in the chain are held together by girdle bands but these bits are very well stuck and it took a long time to find examples. This valve view is quite clearly dumb-bell or 'panduriform' giving a clear assignation. (Modified from Chris Carter.)

References: 
Round, F.E., Crawford, R.M. & Mann, D.G. (1990) The Diatoms: Biology and Morphology of the Genera