DISTRIBUTION 343 



scarce throughout the Cambrian, but in the Ordovician, species and indi- 

 viduals abound. 



In the Lower Cambrian (Olenellus beds); thirteen genera of Brachiopods 

 are represented, occurring both in North America and in Europe. A market! 

 increase is apparent toward the close of the Cambrian, and in the Ordo- 

 vician and Silurian, where the climax of their diversity is reached, upwards 

 of 2600 species are known. These are distributed chiefly in North America 

 and in Europe (Great Britain, Scandinavia, Bohemia, Russia, and Portugal) ; 

 but numerous forms are also found in South America, Australia, China, and 

 Eastern Siberia. 



In the Devonian Brachiopods are scarcely less plentiful than in the 

 Silurian, although a considerable number of genera, especially those belong- 

 ing to the Atremata and Neotremata, have now disappeared. The most noted 

 European localities where Brachiopods abound are the Eifel, Rhineland, West- 

 phalia, the Hartz, Belgium, Devonshire, Boulogne sur Mer, Cabrieres in the 

 Cevennes, the Asturias, and the Ural. Canada and the Middle Western 

 States of North America also yield great quantities of Brachiopods. 



The Carboniferous of North America and its equivalent horizons in 

 Europe and Eastern Asia, together with the so-called Permo-Carboniferous 

 of the Salt Range of India and Armenia, are very rich in Brachiopod remains, 

 especially those belonging to the Productidae, Strophomenidae, Spiriferidae, and 

 Rhynclwnellidae. 



In the European Permian, the number of species of Brachiopods is reduced 

 to about thirty, but in the Salt Range of India greater numbers occur. In 

 the Alpine Trias, the Terebratulidae, fihynchonellidae, and Koninckinidae attain 

 an enormous development. 



The Jurassic and Cretaceous Brachiopods belong almost exclusively to the 

 Terebratulidae, Rhynchonellidae, and the Thecidiidae ; the first two families in 

 particular being represented by an astonishing number of species. The 

 Spiriferacea become extinct in the Lias. 



With the beginning of the Cenozoic era, Brachiopods are no longer a con- 

 spicuous group of fossils. The species occurring in the Tertiary are almost 

 without exception generically identical with those now living, and scarcely 

 exceed them in number. On this account they are devoid of practical 

 interest or importance to the geologist. 



[The credit for having revised and practically rewritten the translation of the entire 

 Brachiopod chapter belongs to Mr. Charles Schuchert, of the United States National Museum. 

 The classification adopted has been taken from his Syno2)sis of American Fossil Brachiopoda, 

 now in press. TRANS.] 



