From the states of Minas Gerias and Bahia, Brazil, Melocactus ernestii is one of the larger Melocactus. It can grow up to 18 inches tall and 14 inches around. It also has some of the longest spines of the genus, one synonym is Melocactus longispinus. This was another Home Depot buy, hopefully it is properly identified. it sure has longer spines than any of my other Melos. Below is a picture of a plant that I beleive to be this species. It was taken at B&B Cactus Farm. I didn't think to look at the tag.