The specimens of S. deltae exhibited shells characterized by their small size, equal valves, sub-trapezoidal shape, elongation, and a thick, coarse, dark epidermis with radiating ribs behind the keel. The front of the valves was rounded, and the ventral margin was convex towards the front and slightly concave towards the rear. A prominent, high, and sharp keel divided the valves into two distinct subdivisions. Each valve measured approximately 13mm in length and 5mm in width.