44 if you count multiple evolutions of one Dex No. eg.
Eevee evolves to Vaporeon and Eevee evolves to Jolteon are counted as 2 or
Alolan Vulpix evolves to Alolan Ninetales and Kanto Vulpix evolves to Kanto Ninetales are also counted as 2.
If you want to count for the amount of base Pokemon, then it is 38. Someone please tell me if I'm wrong.
Source: http://pokemondb.net/evolution/stone
