Shell thin, small (10mm max), hyaline, almost equivalve and equilateral; the lower margin is always semicircular, while the anterior and posterior upper margins are straight. Above: the species in C. W. Thomson: The depths of the sea, London 1874, p.465. The species was named in honour of Sir John Hoskyns the 2nd, one of the founders of the Royal Society, and president of the latter (1682-1683) in succession to the learned and famous architect Christopher Wren.

The lower (right) valve is adorned with narrowly spaced commarginal lirae crossed by minute radial ribs. The upper (left) valve bears, near the umbo, widely spaced commarginal lamellae, quickly replaced by about a dozen of radial rows of semicircular scales.