The table below is a reproduction of part of his statistics as provided in Fergusson's 'Rude Stone Monuments'.

Fergusson himself admitted that 'The information in this table must be received with great limitation. In the first place, What is a dolmen?'...The value of the 'ac' distinction does not come out clearly: first because of the imperfect mode in which it has been contained, but more because it does not make it clear that there are in France twenty-nine departments in which there are no dolmens, and no ac-terminations; in fact, the negative evidence, which does not appear here is stronger than the positive'. (1)

Fergusson continues 'Referring to the table...we find that thirty departments contain more than ten monuments. Thirty others, according to M. Bertrand, contain from one to eight or nine; and the remaining twenty-nine either contain none at all or these are so insignificant as hardly to deserve attention'. (1)

Note - Fergusson mentions that although the termination 'ac' occurs in 'that part of Cornwall south of Redruth and west of Falmouth' (at least 38 times, always spelt with an additional k)...'it is not found anywhere else in Great Britain or Ireland. Nor is it found in the Channel Islands, though dolmens abound there'. He forgets to include those Irish, Welsh and Scottish place names that have terminations of 'ach' etc.

(Prehistoric French Sites)