As an alternative to the initiation of proceedings for the formation of a special service district by resolution or resolutions, a petition may be filed with the secretary of the district signed by voters equal in number to at least 25 percent of the registered voters registered within the proposed special service district as determined from the affidavits of registration. The boundaries of the proposed special service district shall be described in the petition; provided, that when the entire area of a public agency is to be included in the special service district, it may be described by name.