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What is this ?

My son is completing his science project on our local tidepools. We've identified all specimens during our field study, except for the attached. Can you help? 

Andrea, Coal Oil Point - May 9, 2020

Curator Response

Hi Andrea,

This is Norrisia norrisi, commonly known as Norris' Top-shell or Norris's Topsnail.

By the way, on its surface in one of your photos are two Crepidula norrisiarum, also known as slipper limpets.

Stay curious,

Howard/Berry Chair and Curator of Malacology Henry W. Chaney, Ph.D.