This is a purple-ringed top snail, Calliostoma annulatum, the most beautiful shelled snail on the west coast in my opinion. They cruise up and down kelp plants looking for a meal. Generally, they eat what ever is growing on the kelp plants, such as hydriods, bryozoans, diatoms, and copepods. If there is nothing on the kelp plant, they will eat the kelp itself. They have been known to travel 20-30 feet in a twenty-four hour period.