The largest Whelk I am aware of is a Busycon perversum from off Panama City, Florida, collected in shallow water (<3 ft) by Edward Schelling and his daughter Sandy, in about the mid 1970's.
Over 900 mm, yes, over 36 inches...  I saw it (and heard the story) in his shop back in the late 1980s.  It is probably in Sandy's home now.

Leslie

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From: Conchologists List [On Behalf Of Batt, Richard
Sent: Monday, December 28, 2015 6:30 PM
To: [log in to unmask]
Subject: Re: [CONCH-L] A HUGE Lightning Whelk!

 great sizes!  Besides my sinistrum, which at 381.6 mm is only a fraction of a mm larger, my biggest perversum from Mexico is 268.9 mm (and I have a near-albino freak that's 268.1mm)

On Dec 28, 2015, at 5:51 PM, "John Timmerman" <[log in to unmask]> wrote:
From my humble collection - to contribute to the conversation. 
Note: Pay attention to the sources, not the nomenclature as I am sure to be in disagreement with someone. 
 
 Busycon sinistrum  381 mm live, mud flats, Sanibel Island, Florida (purchased – “new” when I got it but now “old collection”)  
 Busycon laeostomum   323 mm  self-collected dead  on beach, North Core Banks, North Carolina
 Busycon laeostomum   285 mm  self- collected very fresh dead, Barden Inlet, Cape Lookout, North Carolina
 Busycon laeostomum  282 mm off Barnegate Light, New Jersey, by commercial fishermen for Scungilli
 Busycon perversum pulleyi  282 mm fresh dead, Texas 
 Busycon perversum perversum, 244 mm  off Yucatan, Mexico  (I am betting there are examples way larger than this)
 
All measured by caliper. 
 ohn Timmerman
 
From: Conchologists List [mailto:[log in to unmask]] On Behalf Of Batt, Richard
Sent: Monday, December 28, 2015 4:03 PM
To: [log in to unmask]
Subject: Re: [CONCH-L] A HUGE Lightning Whelk!
 
It seems to me that the largest ones tend to come from the southwestern coast of Florida?  
I have two others close to that size from the same general area (but I do have a pretty good size one from North Carolina, too).

On Dec 28, 2015, at 3:30 PM, "Bob Winters" <[log in to unmask]> wrote:
lt's Busycon contrarium no matter what WoRMS thinks.
 
On Mon, Dec 28, 2015 at 12:18 PM, Paul Jones <[log in to unmask]> wrote:
Awesome, Richard - both yours and the one at the museum in Sanibel!  
Did the one at the museum actually come from Sanibel Island itself or from somewhere else, I wonder?  AMAZING...
 
Warm regards, Paul
 
On Mon, Dec 28, 2015 at 12:39 PM, Batt, Richard <[log in to unmask]> wrote:
my largest is 381.6 mm from  missouri Key.  My largest dextral one is 271 mm from Crystal River.  
Listed record for typical sinistral is 413.5 mm, at the shell museum on Sanibel.

On Dec 28, 2015, at 11:34 AM, "Bob Winters" <[log in to unmask]> wrote:

Hey Paul,
 Have one here at 365mm from Lee Co., Florida and l've seen larger ones.
 Bob Winters
 
On Mon, Dec 28, 2015 at 8:58 AM, Paul Jones <[log in to unmask]> wrote:
All the recent discussion about sinistral whelks must have been a premonition of sorts.  This past Saturday afternoon, while shelling intertidally around the St. Augustine, Florida Inlet area on the minus tide, I was amazed to come across a day late Christmas gift and prize for the collection:  a huge and alive Busycon contrarium (Conrad, 1840), mostly buried in the sandy mud at the entrance to Comanche Cove Marina, next to the Vilano Beach Bridge.
 
It measured (without digital calipers) right at about 300 mm (12 full inches) in size!  I'm sure it is nowhere near a word record size or anything, but it sure is the largest one I've ever found!   Prior to this one, the largest I had in my collection was about 225 mm (9 inches).  I understand they can reach up to 400 mm!  
I was just wondering what the largest size of this species folks on the list might have in their collections and how my prize stacks up against others finds around its range?   
Wishing a happy shelling 2016 to all, Paul   

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