Amphora coeffeaeformis (Agardh) Kutzing is frequently found in brackish water. However, different concepts of this species found in the literature lead to confusion with respect to its true identity. In this study Agardh's type material from Carlsbad, as well as Kutzing's samples from the same locality, have been examined using light and electron microscopy to establish the true concept of A. Keywords: Amphora coeffeaeformis, Amphora, Agardh, Kutzing, Brackish water, Amphora lineata, Diatoms, Marine Diatioms.