Hi Sylvia,
 
There are quite a few normally sinestral gastropods besides some of the
whelks.  Not being a big marine collector, the first other group that comes to
mind are some of the Turrids, quite a few lefties in that group as I recall.
There are many land snail species which can be included here...many members of
the genus Amphidromus from The Philippines and Indonesia are sinestral(some
species of the genus commonly occur as either right or left!).  Then there are
Euhadra from Japan, certain Camaena from China, some Ariophanta from India,
Bertia and Dyakia from SE Asia and Indonesia, Corona perversa from So.
America, Archachatina bicarinata from West Africa, and the very numerous (200
genera alone, many 100's of species) Clausilidae, or "Door Snails", which are
found mainly in Europe, Asia, and South America. I'd say, according to my
calculations, there's unquestionably a cornucopia of contrarily-coiled
conchiform crawlies!
 
Ken Zentzis
Wichita, Kansas