Can anyone identify these Portland stone fossils?

[tjp@xxxxxxxxxx (Tim Palmer)]

Your fossils are a marine snail (gastropod) which
delights by the scientific name of Aptyxiella
(pronounced ap-tixie-ella) portlandica.  They lived on
the soft sandy sediment in the floors of the shallow
tropical sea that covered this area of Dorset about 130
million years ago when the sediment that is now Portland
Stone was forming.  The shell of these delightful beasts
was made of a form of calcium carbonate called
aragonite.  Aragonite tends to be rather soluble so that
when the shells eventually got buried in the sea-bed and
the sediment started to turn to rock, the shells
dissolved away to leave the moulds (impressions) that we
see today.  Interestingly, the dissolved aragonite then
precipitated as minute crystals of calcite (another form
of calcium carbonate) between the sand grains (called
ooliths) of the rock, and thus provide the natural
cement that hold the rock together.

Aptyxiella portlandica only occurs in the upper bed of
the Portland Stone (the Roach Bed), in the north of the
Isle of Portland, where the water was shallow.  Further
south, the original sea bed sloped off into deeper water
and the animal didn't like the conditions.