Most of the fibulae have a triangular molding above the notch, which probably contained wound wire. The crossbar is decorated either with a flat knob or with a Persian merlon.
1949, N. P. Toll, “Fibulae”, in Teresa G. Frisch, N. P. Toll, edited by M[ikhail] I[vanovich] Rostoftzeff, A. R. Bellinger, F. E. Brown, N. P. Toll, and C. B. Welles, The Excavations at Dura-Europos, Part IV. The Bronze Objects: Fascicle 1. Pierced Bronzes, Enameled Bronzes, and Fibulae, number Final Report IV, New Haven, Conn.: Yale University Press; London: Geoffrey Cumberlege, Oxford University Press, Bow Fibulae, page 56