Where a district boundary line, as appearing on the Zoning Map, divides a lot or land in single ownership as existing at the time of this enactment, the use authorized on and the district requirements applying to the less restricted portion of the property shall be construed as extending into the remaining portion of the property beyond the district boundary lines for a distance not exceeding 35 feet. Otherwise, unless shown to the contrary on the Zoning Map, the boundary lines of districts are the center lines of streets and roads, or such lines extended, railroad right-of-way lines, the center lines of creeks and waterways and/or the corporate limits line of the Town as it existed at the time of the enactment of this chapter.