Shellos

Shellos (Japanese: カラナクシ Karanakushi) is a -Type Pokémon introduced in Generation IV. Its colors differ if it was born on the east or west of Mt. Coronet in Sinnoh.

Physiology
The west sea Shellos is pink with bumps on its back. Both Shellos move like slugs. This is unsurprising, because it is the 'Sea Slug Pokémon'. In all, the West Sea Shellos isn't much different than the east sea Shellos. The east sea Shellos is mostly blue, with a soft green underbelly. There are strange wings on this Shellos' back.

Evolution
Shellos evolves into Gastrodon once it reaches level 30.