public function deleteMarker($index = null)
	{
		$markers = $this->listMarkers();

		if ($index === null)
		{
			$index = count($markers) - 1;
		}

		if ($index >= count($markers) || $index < 0)
		{
			throw new OutOfBoundsException('Marker index out of bounds.');
		}

		$marker = $markers[$index];
		unset($markers[$index]);
		$markers = array_values($markers);
		$this->setOption('markers', $markers);

		return $marker;
	}