G. arcuata is very common in Texas (the so-called "Devil's Toenails") and further north, and there are  other species from parts of the Cretaceous there and in the Western Interior.
Since North America and Europe were still connected until much later in the Cretaceous, and the shallow Western Interior Seaway would have been continuous through Texas and across the Mississippi Embayment aulacogen feature, across Florida and up the east US coast onto GreAt Britain and Europe ( still at the time all part of the same continent) it would make sense that species such as this could have had a continuous distribution.  When I was doing amonite work I came across some shallow-water nektobenthic ammonite species found in both Colorado and Europe, and the shallow nektobenthic ammonites did not undergo any post-mortem transport.

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> On Jan 8, 2016, at 4:56 PM, "[log in to unmask]" <[log in to unmask]> wrote:
> 
> I notice that Grypaea arcuata has been found in Britain and Europe. Would our Gryphaea necessarily be the same species? Were the seas and/or landmasses so connected during or just prior to the Jurassic that the one found in Utah could be from a group that became isolated as the land masses rose, dividing the seas?
> 
> 
> ---- Allen Aigen <[log in to unmask]> wrote: 
> 
> =============
> Gryphaea is marine.  
> Allen 
> 
>      From: "[log in to unmask]" <[log in to unmask]>
> To: [log in to unmask] 
> Sent: Friday, January 8, 2016 10:52 AM
> Subject: Re: [CONCH-L] Fossil snail with operculum-link to photos
> 
> Perhaps they are related. Was G. arcuata a terrestrial, fresh water, or marine critter?
> 
> ---- John Wolff <[log in to unmask]> wrote: 
> 
> =============
> They look like Gryphaea arcuata (Lamarck, 1801) I have from England's 
> Lower Sinemurian, Jurassic (200-150Ma).  I believe they are called 
> "Devils' toenails"
> 
> John
> 
> At 08:33 PM 1/07/16, you wrote:
>> ASU has just received this lovely fossil snail from Fred Skillman, 
>> an amateur entomologist who found it in a wash on private land near 
>> Delicate Arch, Arches National Park, Utah. It is such a treasure for 
>> me because it actually has what appears to be fossilized animal and 
>> an operculum which became separated when he was cleaning off 
>> caked-on dirt. I just had to share with all of you. We think it may 
>> date back to the Jurassic.
>> 
>> To see 5 photos just copy and paste the following link onto your 
>> search engine.
>> 
>> https://drive.google.com/drive/folders/0B-Vz8pRKgeC8M1NLa1k4U2VZNDg=============
>> 
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