Fallacia californica and F. tenera are similar in size and in their coarse areolae. However, F. tenera has a narrower lanceolate lyre-shaped hyaline area, uniform striae along the valve margin (particularly near the central area), a symmetric central area and a single or incomplete double row of areolae along the raphe. Fallacia cryptolyra and F. sublucidula are also small freshwater species with distinct panduriform lyre, but they have fine areolae that are not resolvable in LM.
BioData Reference
Krammer and Lange-Bertalot 2/1 Pl 65 Fig 7-9