Lutraria is a genus of medium-sized marine bivalve mollusks or clams, commonly known as otter shells. Characteristics Members of this genus have large, elongated oval shells with two equal sized valves. The anterior end is somewhat sharply curved but the posterior end is more rounded. The valves gape slightly at both ends, more so at the posterior end. The shell is fairly thick and is sculptured with fine concentric lines corresponding to periods of growth. The basic colour is white and the periostracum is brown, but the latter is usually abraded. The interior surface of the valves is glossy white. The beaks are blunt and situated slightly closer to the anterior end. The ligament is small and largely internal. The foot is small and the siphons are long and are housed in a common horny sheath for most of their length. Biology These mollusks live buried in sand to a depth of about , usually below low water mark, with their siphons extended to the sea bed. As they grow they burrow deeper but are otherwise relatively sedentary. Fossil record Fossils of Lutraria are found in marine strata from the Eocene to the Quaternary (age range: from 33.9 to 0.0 million years ago.). Fossils are known from Europe, South Africa, Japan, New Zealand, Pakistan, Australia, India and Argentina. Species Lutraria angustior Philippi, 1844 Lutraria budkeri Nicklès, 1955 Lutraria capensis Reeve, 1854 Lutraria complanata (Gmelin, 1791) Lutraria curta Reeve, 1854 Lutraria impar Reeve, 1854 Lutraria inhacaensis Boshoff, 1965 Lutraria lutraria (Linnaeus, 1758) Lutraria maxima Jonas, 1844 Lutraria oblonga (Gmelin, 1791) Lutraria rhynchaena Jonas, 1844 Lutraria senegalensis Gray, 1837 Lutraria sieboldii Reeve, 1854 Lutraria steynlussii Huber, 2010 Lutraria turneri Jousseaume, 1891 References Mactridae Bivalve genera Taxa named by Jean-Baptiste Lamarck