I have provided a link to an 'edible' herb that is being sold in a
local Sydney nursery as Aethionema cordifolium or Lebanese Cress. The
photo is all that I have for now, until it flowers.

http://www.box.net/shared/static/cssjc2rdoj.JPG

I queried the identification with the manager, but got the answer
"Well, that's what we were told it is."

Clearly the plant being sold is not the same as that described at

http://www.robsplants.com/plants/AethiCordi.php

So what species is being sold in the nursery? And is it harmful to
health?

It does not look like a member of the Brassicaceae family, rather a
member of the Apiaceae, aka Umbelliferae.

Perhaps Berula erecta?

http://commons.wikimedia.org/wiki/Im...la_erecta0.jpg

If it is B. erecta then there seem to be reasons for caution if
selling it as an edible herb.

http://vm.cfsan.fda.gov/~djw/pltx.cg...=berula+erecta

Has anybody any comments?

The same nursery, different staff, was selling this so-called Lebanese
cress in 1999, and I tried to pursue identification then. Back then my
plant flowered with typical Apiaceae umbels, but I can't remember the
details.