Shell thin, hyaline, longer posteriorly. Hinge with teeth in subequal series, separated by smooth gap. Ligament external, opisthodetic, sunken in a groove. Siphons present, inhalant and exhalant siphons fused together but open ventrally.
This genus was synonymized with Malletia by Sanders and Allen (1985), but because of its size and tightly closed valves, we leave it separate and in the Neilonellidae. The name is based on the American malacologist W. J. Clench; the gender is feminine.