Hi, David. This may not be what you need, or you may have found
it already, but there is a wonderful book on the patterns in
seashells and how they are created by Heinz Meinhert - a new
edition just came out. It has some of the world's most beautiful
shells and an analysis of their patterns - mathematically too.
Great charts and photographs. ( I now have it at home from the
library - let me know if you want rest of reference details).
Among the shells pictured are oliva porphyria ( famous tent
olive), thatcheri mirabilis (I understand many vote that as the
most stunning shells), and many voluta species.
 
- Karen VV