Plesiosaur us

(ples-e-o-sau'rus.) [From Gr. plesios, near, and sauros, a lizard.] (Zool.) The name of an extinct genus of marine Saurians, remarkable principally for their length of neck. The species are found in the Lias, Oölite, and Cretaceous measures, and were 25 to 40 feet long. [s. 716]