Higher Pokedex Pokemon missing from Pokemon Go? [duplicate]

Solution 1:

Prior to the second generation update

Nearly all the Pokémon from the second generation are not included yet in the game. The only second generation Pokémon present at the moment are the following:

• Pichu (#172)
• Cleffa (#173)
• Igglybuff (#174)
• Togepi (#175)
• Togetic (#176)
• Smoochum (#238)
• Elekid (#239)
• Magby (#240)

Magby being #240, it's the highest you can reach right now in the Pokédex. The highest you could reach before was Dragonite which is #149. So everything above #149 is missing in the game at the moment, except for the ones from the list above.

Since second generation update

It has now been possible to catch pretty much all the Pokémon of the second generation up to Ho-Oh, which is #250. Celebi is still missing.