The olfactory organ of the snapping turtle includes two types of sensory epithelia.
One of them contains ciliated receptor neurons which send axons to the ventral OB.
The other contains non-ciliated receptor neurons which send axons to the dorsal OB.
G proteins were expressed similarly, but glycoconjugates were expressed differently.
One might sense odors in the air, and the other might sense odors in the water.