A removably mountable electrothermal print head for writing dots-matrix characters while moving along a thermosensitive recording medium and a mounting for the hand or a movable carriage of a printer, the head comprises a plurality of electrically energizable resistive printing elements coated on a support; the outer surface of said elements is partly cylindrical with the generatrices in parallel relation with a common direction which is transversal with respect to the printing line of the recording medium. The print head is positioned with respect to the recording medium with the part-cylindrical outer surface of the resistive printing elements in tangential relation with the recording medium. The printing head is positioned on and removably fixed to the carriage by a manually actuatable latch.