Scapharca (=arca) chemnitzii (Phillipi, 1851) - Chemnitzi’s Ark

The Scapharca chemnitzii shell is up to 4 cm long and almost just as high. It is thick, sturdy, inflated (convex), equivalve (very slightly inequivalve) and inequilateral (beaks slightly anterior to midline- cf. Sc. Brasiliana which has the beaks more in the middle). It is roughly squarish in shape, the posterior end not so long as in Noetia centrota and Anadara ovalis. It beaks much more widely separated than in the other species (including Sc. Brasiliana), thus exposing a fairly large (and striated) cardinal area. Its color is usually white, but can also be a light brown or grey; banded specimens may occur. Its periostracum is thick, velvety, and reddish-brown in color and often remains in the radial grooves long after death. The surface sculptured by about 28 strong, transversely grooved and beaded (cf. Anadara ovalis) radial ribs. Growth stages are usually prominent. Hinge line with 25-50 teeth the larger specimens usually possessing more. It is fairly common, live specimens often being washed up or found at low tide in the East beach mudflats.