At Thorpe, near Aldborough, and at Southwold, in Suffolk, this fluvio-marine formation is well exposed in the sea-cliffs, consisting of sand, shingle, loam, and laminated clay. Some of the strata there bear the marks of tranquil deposition, and in one section a thickness of 40 feet is sometimes exposed to view. Some of the lamellibranchiate shells have both valves united, although mixed with land and freshwater testacea, and with the bones and teeth of elephant, rhinoceros, horse, and deer. Captain Alexander, with whom I examined these strata in 1835, showed me a bed rich in marine shells, in which he had found a large specimen of the _Fusus striatus_, filled with sand, and in the interior of which was the tooth of a horse. Among the freshwater shells I obtained the _Cyrena consobrina_ (fig. 26. p. 28.), before mentioned, supposed to agree with a species now living in the Nile. I formerly classed the Norwich Crag as older Pliocene, conceiving that more than a third of the fossil testacea were extinct; but there now seems good reason for believing that several of the rarer shells obtained from these strata do not really belong to a contemporary fauna, but have been washed out of the older beds of the "Red Crag;" while other species, once supposed to have died out, have lately been met with living in the British seas. According to Mr. Searles Wood, the total number of marine species does not exceed seventy-six, of which one tenth only are extinct. Of the fourteen associated freshwater shells, all the species appear to be living. Strata containing the same shells as those near Norwich have been found by Mr. Bean, at Bridlington, in Yorkshire. _Newer Pliocene strata of Sicily._--In no part of Europe are the Newer Pliocene formations seen to enter so largely into the structure of the earth's crust, or to rise to such heights above the level of the sea, as in Sicily. They cover nearly half the island, and near its centre, at Castrogiovanni, they reach an elevation of 3000 feet. They consist principally of two divisions, the upper calcareous, the lower argillaceous, both of which may be seen at Syracuse, Girgenti, and Castrogiovanni. According to Philippi, to whom we are indebted for the best account of the tertiary shells of this island, thirty-five species out of one hundred and twenty-four obtained from the beds in central Sicily are extinct. Of the remainder, which still live, five species are no longer inhabitants of the Mediterranean. When I visited Sicily in 1828 I estimated the proportion of living species as somewhat greater, partly because I confounded with the tertiary formation of central Sicily the strata at the base of Etna, and some other localities, where the fossils are now proved to agree entirely with the present Mediterranean fauna.