A SYNOPSIS OF A31ERTCAN FOSSIL BRACHIOPODA. 

 INCLUDING BIBLIOGRAPHY AND SYNONYMY. 



By Charles Schuchebt. 



CHAPTER I. 



GF.OT.OGTC DEVELOPMENT AND GEOGRAPHIC DISTRIBU- 

 TION OF AMERICAN FOSSIL BRACHIOPODA. 



GEOLOGIC DEVELOPMENT. 



Upward of 2,500 species of bracliiopods have been described or 

 identified from the sediments of the IS^orth and South American con- 

 tinents and adjacent islands. Of these, -5,053 are recoguized in this 

 catalogue, the other species, about 20 i)er cent, beiug considered as 

 synouj'ms. 



Little is known of the fossil forms from South America. Forty-eight 

 genera are represented by 159 species, ranging from the Cambrian 

 upward. Of these, 125 are from the Paleozoic and 31 from the Meso- 

 zoic. The Cambrian, Ordovician, and Jurassic brachiopods require 

 further study, since authors have given little or no attention to their 

 internal characters, and also have too readily identified them with 

 well-known European sj^ecies. 



In North America there are 1,922 species, of which 1 ,859 are restricted 

 to the Paleozoic. In 1880 Zittel,' on the basis of Bigsby's Thesaurus, 

 gave a total of 4,213 species of I*aleozoic Brachiopoda. Since Bigsby's 

 compilation the total has probably been increased to 0,000 species, 

 about one-third of which occur in North America. On account of 

 tbeir good preservation and great abundance, both in species and indi- 

 viduals, throughout the Paleozoic, the brachiopods in North America 

 are of particular value in stratigraphic and correlati\e geolog}'. 



In the Mesozoic there is a remarkable scarcity of brachiopods, since 

 but 49 species have been recorded, and many of these are rare. The 

 Cenozoic representation is even smaller, there being but 11 species. 

 This scarcity of post Paleozoic brachiopods is very apparent in the 

 oldest system of the ]\Iesozoic, the Triassic, from which but 11 species 

 have been described, whereas in the Carboniferous there are 478 



'Handbuch der Palaeontoloiiie, Vol. I, 1880, pp. 709-710. 



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