Unknown shell #1 - SEA OF CORTEZ

[bidd40]

I have 5 shell books and cannot find this shell in any of them.  Caught in fishing nets from the northern part of the Sea of Cortez.
I will be supplying many species endemic to the Sea of Cortez in the future, so don't hesitate to contact me if your looking for anything special.
I am supplying sea urchins, seafans, sand dollars - especially clypeaster europacificus - 200mm/8" and larger in size.  Sea shells of many different species.  Sea Stars, corals, and anything on anyones want list.
I have great contacts with actual fishing & shrimp boat captains.
For a sample see my Ebay listings at - danroxy2001
I just started supplying shells and other specimens and am going to have many, many more available very soon.
Thanks you for any help in identifying this species.
Feel free to contact me by regular email if you need more pictures - <!-- e --><a href="mailto:bigd40@cox.net">bigd40@cox.net</a><!-- e -->
Daniel Notek

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[paul monfils]

This is Bursa nana.