Jamaican Cookery yams

Yellow yam

Negro yam

Lucea yam

Indian yam

Hard yam

Jamaican white yam

Guinea or water yam

These are pictures of the yams Caroline Sullivan mentions in the Jamaica Cookery Book. I believe the Indian yam is the closest to the type of yam that would lead to the origins of my wife's "sweet potato" recipe that may or may not actually be a yam.