The Troca Shell is a top shell, scientific name: Trochidae. This is a large family of shells found world wide. The shells are spiral to conical shape and vary from low to tall and slender. They range from less than 1/2 inch to over 6 inches in size. The shells exterior are variable and may be smooth, glossy or sculptured. All trocas have a pearly interior and a horny operculum consisting of many turns.