It is the duty of the tax assessor of every county in the state to procure at the expense of the county a book in the form to be prescribed by the Department of Revenue, in which he shall enter a complete map and list of all the blocks and lots which have been platted, and the maps of which are recorded in the office of the judge of probate or can be procured within his county, beginning with the lowest numbered block and lot and proceeding in numerical order to the highest, with the name of the owner set opposite each block and lot. Each subdivision or addition to any town or city shall be shown by proper headings at the top of each page of such lot book and by index in the front thereof. The tax assessor shall annually make the entries thereon, for which he shall be allowed a reasonable compensation to be fixed by the governing body of the county at not less than $150 for each book of 400 pages or more; provided, that in Jefferson County, the tax assessor shall keep map books as above prescribed which shall only show the unit number of each and every parcel of property and shall show annually any change in any unit number, but not otherwise; provided, that in any county where the tax assessor is on a salary basis, the additional compensation provided for in this section shall not be applicable.