The Northern Quahog
The Northern Quahog, Mercenaria mercenaria (Linnaeus, 1758), measures up to 120 mm (about five inches). Its shell is trigonal to rounded, with commarginal ("concentric") ridges on the outer surface. It differs from its closest relative (and local native species), the Southern Quahog, Mercenaria campechiensis, by smaller maximum size, lack of commarginal ridges on central part of the external shell surface, and, most of all, by the violet-color tinges on the internal surface o