Good question. 'Argyraeus', originally a wild collected plant named var. argyraeus was described as
supra argyraeo-maculata (silver spotted above). This is the definition used by some like the RHS. Others, including MOBOT, define it as "...leaves have silver-white edges..."
Descriptions of both 'Argyraeus' and 'Exotica' ('Exoticus') can be found in Hatch's Perennials describing 'Argyraeus' as have more silver spots than wild collected plants (due to selection of cultivated plants over the years) with 'Exoticus' ('Exotica') being mostly silver with a central green tree.
Some links:
Original description of var. argyraeus'.
https://archive.org/stream/mob... (page 13)
MOBOT:
http://www.missouribotanicalga... I've asked the folks at MOBOT if they clarify this but didn't receive a reply.
RHS:
https://www.rhs.org.uk/Plants/...
Hatch:
http://members.tripod.com/~Hat... (search argyraeus).
Satin Pothos (Scindapsus pictus 'Exotica')
edited
