Didn't mean to ignore your comment for 10 months, I must have forgotten to reply. I was mainly referring to the evolved forms to save space, since Ekans evolves into Arbok. And I guess technically Onix is a rock snake, and he's in the game...
What does that mean? I only have a regional Pokédex. It means he's afraid of Snake Pokémon... It does not! Stop it Patrick, you're scaring him! O~o~h! Arbok. Seviper! Serperior.