The Countryside Council for Wales confirmed the discovery, but is keeping the location of the fungi secret.
"It is amazing that we found two new species so close to each other," said Dr Rhind.
'Rarities'
"We will be keeping the sites secret at the moment so that these rarities can be studied in more details and allowed to flourish."
As the toadstools have never been seen in Britain, they do not have English or Welsh names and are referred to by their Latin names.
Agaricus koelerionensis belongs to the same family as the mushrooms you would buy in a shop, except that this one is not edible.
It is uncommon throughout northern Europe but can be identified by its umbrella shaped cap which has lilac tints and a dullish pink stem.
Discovered by Helen Hughes of CCW and Maurice Rotheroe from the British Mycological Society, the fungi is associated with grassy or sandy areas.
Bluish tints
The colourful Russula torulosa has a shiny purple cap and short stem with bluish tints.
One of its most distinguishing features is its strong smell of fresh apples.
In Europe it is mainly found under pine trees on sandy soils or on limestone.
The Russula torulosa was discovered by fungus expert Geoff Kibby.
"Why these species have turned up in Wales is open to speculation, but up until quite recently not much work has been done looking for fungus on our sand dunes," said Mr Kibby.
"These new discoveries suggest that we do indeed need to carry out further survey work across Wales.
"We may find that Wales has many more rarities waiting to be found!" added Dr Rhind.