Abstract
This study was carried out on an epilithic sample obtained from a stretch of river, dozens of miles up from the Fair River estuary in North Carolina, USA. Light microphotographs of 275 valves of Navicula tenelloides Hustedt were analyzed. Generally, the overall form of these valves were lanceolate (69.0%) with acute ends (70.5%) and small central area (87.1%). Such morphological variability is not shown in either the original description by Hustedt (1937) or the holotype's photo by Simonsen (1987). However, we identified our specimens as Navicula tenelloides, because some specimens from this single assemblage shared several other characteristics with Hustedt's specimen, namely size (length and breadth), density of striae, degree of protrusion at the ends of the valve, shape of the central area and striae arrangement.
