Although all Conus have a poison injecting apparatus, only a few are
considered dangerous to human beings.  The key is what they eat.
Conus species that feed on small worms and other invertebrates have a
radular "dart" just large enough and a venom just powerful enough to
kill such small feeble prey.  Such cones are harmless to people.  It
is the fish-eating cones that are dangerous.  They have a large dart
(more like a small harpoon). Also, they either have a more potent
venom, or inject a much greater dose of venom, or both (I'm not sure
which of these best describes the actual fact).  This enables them to
rapidly incapacitate a living fish.  It also makes them dangerous to
humans.  The "big three" of course are Conus geographus, Conus
striatus, and Conus textile.  But there are a number of others that
are potentially dangerous, even though they have not caused human
deaths.  Conus tulipa is one that comes to mind, and a few others - I
don't have reference materials here at work.  I wouldn't expect Conus
perplexus to be dangerous.  The fish-eating cones tend to have a wide
aperture, which enables them to swallow a fish after harpooning it.
One word of caution - it is always possible that a particular person
might have an individual sensitivity to Conus venom, just as some
people are hypersensitive to bee venom.  In such a case, any cone
capable of penetrating the skin could theoretically be dangerous.
Paul M.
Rhode Island, U.S.A.