A modular disc cutterbar utilizes self-contained cutter modules clamped between alternating spacer modules by fasteners engaged with the spacer modules. To resist bending moments in the cutterbar, selected fasteners can have a length to span more than one cutter module. The drive mechanism is also of a modular construction including a symmetrical, reversible sealed drive apparatus within each cutter module and a transfer shaft passing through each interstitial spacer module to interconnect each cutter module drive mechanism. The drive apparatus incorporates an oil slinger to keep the remote seals lubricated. The rock guard for each cutter module is mounted on the adjacent spacer modules, while the skid shoe mounting is simplified. A crop mover mounted on each disc member above the cutting knife improves the transfer of severed crop material. An oil slinger mounted on the drive assembly within the cutter module draws oil from the reservoir past the adjacent bearing and disperses the oil onto the corresponding seal member for lubrication and cooling thereof.