A surgical instrument for surgically joining tissue comprising: a handle assembly including a movable handle; a drive assembly disposed in mechanical cooperation with the movable handle; an endoscopic portion extending distally from the handle assembly and defining a first longitudinal axis; a pair of jaw members disposed adjacent a distal end of the endoscopic portion and extending generally distally therefrom, each of the jaw members being curved with respect to the longitudinal axis (A-A), at least one of the jaw members being movable with respect to the other between an open position and an approximated position for engaging body tissue therebetween, the pair of jaw members including a first jaw member and a second jaw member; an asymmetrical dynamic clamping member disposed in mechanical cooperation with a distal portion of the drive assembly, wherein the dynamic clamping member is advanced distally through at least a portion of the length of the jaw members in response to at least a partial actuation of the movable handle, the dynamic clamping member including an upper beam, a lower beam, and a vertical portion, the vertical portion having a width equal to the drive beam and connecting the upper beam and the lower beam, the vertical portion including a cutting edge on its distal face; and a tissue stop disposed adjacent a distal portion of the first jaw member and configured to impede tissue from escaping the jaw members, characterised in that a transverse cross-sectional shape of the upper beam comprises an upper and a lower planar surface (606b1, 606b2) and a transverse cross-sectional shape of the lower beam comprises an upper planar surface (606c1) and a lower arcuate surface (606c2), and wherein the transverse cross-sectional height (T L) of the lower beam is greater than the transverse cross-sectional height (T U) of the upper beam. a handle assembly including a movable handle; a drive assembly disposed in mechanical cooperation with the movable handle; an endoscopic portion extending distally from the handle assembly and defining a first longitudinal axis; a pair of jaw members disposed adjacent a distal end of the endoscopic portion and extending generally distally therefrom, each of the jaw members being curved with respect to the longitudinal axis (A-A), at least one of the jaw members being movable with respect to the other between an open position and an approximated position for engaging body tissue therebetween, the pair of jaw members including a first jaw member and a second jaw member; an asymmetrical dynamic clamping member disposed in mechanical cooperation with a distal portion of the drive assembly, wherein the dynamic clamping member is advanced distally through at least a portion of the length of the jaw members in response to at least a partial actuation of the movable handle, the dynamic clamping member including an upper beam, a lower beam, and a vertical portion, the vertical portion having a width equal to the drive beam and connecting the upper beam and the lower beam, the vertical portion including a cutting edge on its distal face; and a tissue stop disposed adjacent a distal portion of the first jaw member and configured to impede tissue from escaping the jaw members, characterised in that a transverse cross-sectional shape of the upper beam comprises an upper and a lower planar surface (606b1, 606b2) and a transverse cross-sectional shape of the lower beam comprises an upper planar surface (606c1) and a lower arcuate surface (606c2), and wherein the transverse cross-sectional height (T L) of the lower beam is greater than the transverse cross-sectional height (T U) of the upper beam.