Thats a really nice collection you have there, Eric, in a wide range of very nice colours.
I'd love to have those in my garden!
RE: 
H. corsicus is a synonym for H. argutifolius
I thought so. Thats cleared that up!
On a search on H. corsicus using the RHS button in GA100S36, the RHS website brings up:
Helleborus
argutifolius  (H4) 55 supplier(s) 
corsicus 'Marble' (v) 1 supplier(s) 
That does indeed suggest that H. corsicus is a synonmy and H. argutifolius is the "name of the moment" 
But interestingly, the species corsicus is still used for the cultivar 'Marble'
Suffice to say, its a lovely plant, with very handsome foliage all year, and absolutely masses of those pale green/yellowish flowers.
I have it planted beside Camellias. I think its a good companion colour for the reds and pinks.