An ultrasonic surgical probe has an elongate shaft and a probe head that is enlarged to extend laterally or transversely in two opposed directions relative to the shaft The head is formed with a recess or cavity facing laterally in a third direction relative to the shaft and the axis. Where the head lies in a plane, owing to its lateral enlargement or extension, the recess or cavity faces in a direction perpendicular to that plane. The recess or cavity is defined in part by an inclined floor or base surface contiguous at a proximal end with the shaft. The recess or cavity is defined in part by a peripheral wall extending only partway around the recess or cavity, along a distal side and two lateral sides thereof. The cavity or recess is closed on a proximal side by the inclined surface and the shaft.