Answer:
Reiger dorsal nasal flap: this flap is based on the branches of the angular artery as it descends along the base of the nasal wall to approach the medial canthal area
Marchac’s frontonasal flap: entire nasal dorsum undermined to allow freedom of downward movement (care must be taken to avoid severing the cutaneous branches of the angular artery as the distal portion of the flap is unreliable on the basis of dermal circulation alone), but flap can be back cut, however, to be supplied only by the cutaneous arterial branch that exits from the angular artery near the medial canthus.
See page 1936 in McCarthy for reference.