Dear Sarah (and other interested parties!);
        We have an abundance of Ilynassa up here in New Scotland, both trivial
and obsolete.   obsoleta likes to live in the upper third of the
intertidal range of silty/sandy protected shores, and has a good
tolerance for brackish water, so is often , but not exclusively, found
in salt marshes, or near where a stream enters the ocean- ie, brackish
habitats.  I think it is a detritivore, feeding on pretty-well whatever
comes its way, which means it is an important part of the shoreline's
"rec%cling" system.  As far as its importance to man, it is an abundant
species which helps signifigantly in maintaining the ecological health
of several intertidal habitats, therefore it has good "ecological
value", since our health as humans ultimately depends in large measure
upon the health of the entire biosphere, to which I. obsoleta makes a
good contribution by recycling nutrients, and being an important part of
several food chains (for example, it is eaten by some shore birds,
although i do not know which ones).  So far as "triva" goes, it buries
itself at low tide, and at nearly the EXACT moment the tide starts to
return, nearly all the I. obsoleta on a given shore will emerge from the
sand, at the same time!!  How they do this , i do not know, but it is
fun to watch!
                                                                                                                -Ross M.