Mark -
Sorry - I deleted your message before noting it's title.  But Turridae and
Terebridae also use a "poison dart" (radular tooth and poison sac) to kill
their prey, though none of them are known to be dangerous to humans.  This is
in keeping with the general plan seen in Conidae - the potency of the venom
system is related to the type of prey eaten.  It is the fish-eating cones that
have the most potent poison, while those that feed on small worms and other
invertebrates do not.  Since the turrids and augers feed only on small soft
prey, you might expect a rather weak venom and relatively poorly developed
delivery system, and that turns out to be the case.
 
Paul M.