many thanks for locating that link Anne, showing what appears to be an identical shape, and described as a sugar bowl, which it may well in fact be, rather than a posy - in both the marbled pale blue and 'teal' (though it looks more like purple marbling). In fact I'd not seen the link, so appreciate you efforts with this information.
Your link provides the names of three U.K. C19 manufacturers, as having a connection with this design - Davidson, Sowerby and Hepple - so we're spoilt for choice, though it remains questionable whether this piece is related to any of them, and I'd have thought had there been a connection with those makers then someone here would have commented by now.
The reference to Hepple is obvious - they made similar pressed designs in the shape of small shell-like pieces, though not as far as I know in marbled coloured glass - theirs were in an opal white, and can be seen on the Board's archive for that maker, and in some of the better books on pressed glass.
Both Davidson and Sowerby - plus others - made marbled coloured glass, so always possible this design might have come from them, but in the absence of marks and input from other people here, then attribution remains presently unconfirmed.
For those who may not be aware, the Mods. received a complaint regarding my text of the original post, above, and they have now amended the wording to remove what was described as derogatory and potentially offensive material.
In the light of this I quite naturally apologise sincerely, and can assure everyone that the act of being offensive intentionally could not have been further from my mind.
I won't contribute further, and hope that eventually the correct attribution for this little nautilus bowl will be found. Regards Paul.