THE PLIOCENE PERIOD. 325 



Arvernensis), which is hitherto the only Mastodon found in 

 Britain. 



According to the most recent views of high authorities, 

 certain deposits such as the so-called " Bridlington Crag " of 

 Yorkshire, and the " Chillesford beds " of Suffolk are to be 

 also included in the Newer Pliocene, upon the ground that 

 they contain a small proportion of extinct shells. Our know- 

 ledge, however, of the existing Mclluscan fauna, is still so far 

 incomplete, that it may reasonably be doubted if these sup- 

 posed extinct forms have actually made their final disappear- 

 ance, whilst the strata in question have a strong natural con- 

 nection with the " Glacial deposits," as shown by the number 

 of Arctic Mollusca which they contain. Here, therefore, these 

 beds will be included in the Post-Pliocene series, in spite of 

 the fact that some of their species of shells are not known to 

 exist at the present day. 



The following are the more important Pliocene deposits 

 which have been hitherto recognised out of Britain: 



1. In the neighbourhood of Antwerp occur certain " crags," 

 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, 



