Femtosecond degenerate four-wave mixing experiment (FWM) has been performed at 11 K in transmission geometry, on bulk GaAs as a continuous function of the sample thickness. The FWM signals exhibit the transition from the real, excitonic regime to the virtual regime as the thickness increases from 3 micrometers to 17.5 micrometers . The results at the negative time delay show an extraordinary signal where the energy extends well above the bandedge in FWM transmittance although the thickness is an order of magnitude larger than the penetration depth. These above-the-band-gap signals are mostly confined to the negative time delay region and as the detection energy increases, so does the value of the negative time delay at which the signal peaks. These unusual phenomena can be understood by the third order frequency mixing (2(omega) 2-(omega) 1; (omega) 2>(omega) 1) between positively chirped spectral components.