Identification of this Harpidae?

[staffie2001uk]

This shell, aquired by my girlfried at a car boot sale today, appears to be a harpidae, but I can get no further in identifying it.  All help would be gratefully received.  

<a href="http://www.badongo.com/pic/4079502" target="_blank"><!-- m --><a class="postlink" href="http://www.badongo.com/pic/4079502">http://www.badongo.com/pic/4079502</a><!-- m --></a>

<a href="http://www.badongo.com/pic/4079520" target="_blank"><!-- m --><a class="postlink" href="http://www.badongo.com/pic/4079520">http://www.badongo.com/pic/4079520</a><!-- m --></a>

<a href="http://www.badongo.com/pic/4079522" target="_blank"><!-- m --><a class="postlink" href="http://www.badongo.com/pic/4079522">http://www.badongo.com/pic/4079522</a><!-- m --></a>