From Bulbapedia, the community-driven Pokémon encyclopedia.
In each Pokémon game of Generation V, all Pokémon have an unseen index number used to identify them in the game's ROM. All of them are in their National Pokédex order. Numbers 652 to 684 were added in Pokémon Black 2 and White 2 and are empty in Pokémon Black and White.
Generation IV hybrids do not exist in Generation V because with the exception of ----- the game withdraws the information for the species pointers associated with index number modulo 651.
List of Pokémon by index number
Pokéstar Studios opponents