FIGURE 10. Transitional forms between Flexicalymene senaria and F. trentonensis. These specimens have a somewhat broader anterior border than the neotype of F. senaria (but not as broad as F. trentonensis), a small swelling at the genal angle (but not a full spine, see arrows), and six axial rings on the pygidium (asterisks). The hypostome from Chazy, NY, however, aligns the occurrence there with F. senaria. A. Specimen collected by Walcott, and most likely from the Walcott-Rust Quarry, NY (see text), MCZ 186418, scale bar = 4 mm. B. Specimen from the Lindsay Formation, Ontario, AMNH-FI-140957, scale bar = 5 mm. C–E. Specimens collected from the late Sandbian Glens Fall Formation near Chazy, NY. AMNH locality 4066. C. Cranidium, AMNH-FI-136842, scale bar = 2 mm. D. Pygidium, AMNH-FI-136841, scale bar = 2 mm. E. Hypostome, AMNH-FI-136868, scale bar = 500 µm. See also Whiteley et al., 2002: pl. 68.