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408 represented it, and that the formation in which it was found was the one indicated by Rogers as No. XI. Its interest has since been diminished by the discovery and authentication of fossils of air-breathers in still older formations. Another series of papers of peculiar interest was that concerning the fossil saurian of the new red sandstone (Clepsysaurus Pennsylvanicus).

Having retired from business in 1851, Dr. Lea made another visit to Europe in 1852. Many of the incidents of his previous visit were substantially repeated, but in large part with naturalists of another generation than those whom he had met before. At Paris he arranged and named the Unionidæ in the cabinets of the eminent conchologists Boivin and Petit. He called upon Dr. Chenu to look for the original specimen of Mulleria of Ferussac, which had never been figured, but simply described as being in Lamarck's collection. "He told Dr. Chenu that he thought it must have been mixed with the Etheria, of which the collection had many specimens. Dr. Chenu declared this could not be so, or he would have seen it. As soon as he pulled out the drawer, Dr. Lea saw at a glance the identical specimen which Ferussac had described. He took it up and declared this to be it. Both the naturalists were surprised and delighted. ... Thus Dr. Lea's theory of the genus Acostea, of D'Orbigny, was complete—it was a Mulleria." At Vienna he showed the Austrian naturalists some features in their species and specimens which had escaped their eyes. At Berlin he found Humboldt and other distinguished men of science much interested in what was going on in geology in the United States. At a dinner with the Philosophical Club in London, Sir Charles Lyell gave him credit for being the first and only one who had yet observed an air-breathing animal in so ancient a rock as that in which the Sauropus primævus occurred, and added that the Clepsysaurus Pennsylvanicus was the first discovery of bones in the new red sandstone, although a jaw of a similar animal had since been found. Colonel Sabine exhibited a bottle which he supposed had come through Behring Strait from Japan, which Dr. Lea was able to claim as a verification of his theory of a west-to-east Arctic current.

On his return home in November, 1853, Dr. Lea found an accumulation of correspondence and specimens awaiting his attention that hardly diminished, so incessant were the fresh arrivals, during the remainder of his active life, or for twenty-five years. Among his new Southern and Southwestern correspondents was Bishop Elliott, of Georgia, who became greatly interested in the mollusca of that State, and engaged others in interest in the subject and in collecting shells. The scientific researches of Dr. Lea were continued, with constant publications, until 1877, when a sudden illness which came upon him in Southern California disabled him from further vigorous work. He still, however, continued to add to his collections and perform such work upon them as his strength would allow. He gave much attention