THE PLIOCENE PERIOD. 3S7 



which are the equivalent of the White and Red Crag in part. 

 The lowest of these contains less than 50 per cent, and the 

 highest 60 per cent, of existing species of shells, the remainder 

 being extinct. 



2. Bordering the chain of the Apennines, in Italy, on both 

 sides is a series of low hills made up of Tertiary strata, which 

 are known as the Sub-Apennine beds. Part of these is of 

 Miocene age, part is Older Pliocene, and a portion is Newer 

 Pliocene. The Older Pliocene portion of the Sub-Apennines 

 consists of blue or brown marls, which sometimes attain a 

 thickness of 2000 feet. 



3. In the valley of the Arno, above Florence, are both 

 Older and Newer Pliocene strata. The former consist of blue 

 clays and lignites, with an abundance of plants. The latter 

 consist of sands and conglomerates, with remains of large Car- 

 nivorous Mammals, Mastodon, Elephant, Rhinoceros, Hippo- 

 potamus, &c.' 



4. In Sicily, Newer Pliocene strata are probably more largely 

 developed than anywhere else in the world, rising sometimes 

 to a height of 3000 feet above the sea. The series consists 

 of clays, marls, sands, and conglomerates, capped by a com- 

 pact limestone, which attains a thickness of from 700 to 800 

 feet. The fossils of these beds belong almost entirely to living 

 species, one of the commonest being the Great Scallop of the 

 Mediterranean (Pecten Jacobaus). 



5. Occupying an extensive area round the Caspian, Aral, 

 and Azof Seas, are Pliocene deposits known as the " Aralo- 

 Caspian " beds. The fossils in these beds are partly fresh- 

 water, partly marine, and partly intermediate in character, and 

 they are in great part identical with -species now inhabiting 

 the Caspian. The entire formation appears to indicate the 

 former existence of a great sheet of brackish water, forming an 

 inland sea, like the Caspian, but as large as, or larger than, the 

 Mediterranean. 



6. In the United States, strata of Pliocene age are found in 

 North and South Carolina. They consist of sands and clays, 

 with numerous fossils, chiefly Molluscs and Echinoderms. 

 From 40 to 60 per cent of the fossils belong to existing 

 species. On the Loup Fork of the river Platte, in the Upper 

 Missouri region, are strata which are also believed to be refer- 

 able to the Pliocene period, and probably to its upper division. 

 They are from 300 to 400 feet thick, and contain land-shells, 



22 



