Differentiating between Cepaea nemoralis and Cepaea hortensis

Snails have captured my attention lately and I am getting more and more curious as time goes on.
It isn’t like my curiosity has suddenly been triggered, but rather, it has grown over the past year or so. This curiosity and interest tends to fall back to one or two specific species which I encounter most often. They are the common species in my area of Southern Ontario in the Cepaea genus, Cepaea hortensis and Cepaea nemoralis. But how do you tell them apart?
There is one way to know, but it can be a bit tricky.