14 SYNOPSIS OF AMERICAN FOSSIL BRACHIOPODA. Ibuix. 87. 



species. In marked contrast, also, is this lack of brachiopod conti- 

 nuity wlion compared with the Alpine Trias, from whicli llittner has 

 described .'iSO species; but nowhere else is this system known to have 

 so large a development. This evidence not only indicates a decadence 

 of the class during late Paleozoic, but epeirogenic movements as well 

 near the close of the American Carboniferous, for none of the 478 

 species of this sj'stem pass into the Trias. 



With the Trias a new facies of brachiopod life is initiated; many of 

 the familiar types of Paleozoic shells had, at that time, long since 

 ceased to live or had ended in the Carboniferous or Permian. The 

 superfamilies Acrotretacea, Obolacea, and Pentameracea have died 

 out, while the Lingulacea, Discinacea, Craniacea, Strophomenacea, and 

 Spiriferacea are sparingly represented, and commonly by small species. 

 Before the close of the Jurassic system the Spiriferacea also disap- 

 peared, so that since the Cretaceous era the class is practically repre- 

 sented by rhynchonellas and terebratulas, with a few scattering species 

 of Lingula, Crania, and Discinisca. 



In the American Jurassic there are but 13 species, and all are rare. 

 How remarkable is this representation when contrasted with the Jura 

 of Europe, where certain beds of the Lias, Dogger, and Malm terranes 

 contain millions of specimens of a few species belonging to the families 

 Terebratulidfe and Rhynchonellidai'.' The Cretaceous has 26 species, 

 also a meager representation, and yet " outside of Europe-, North America 

 is the most im])ortant for the occurrence of Cretaceous Brachiopoda."'^ 

 The American Eocene has 9 species and the Neocene 5. The disparity 

 between the European and American Cenozoic brachiopod faunas is 

 partly due to the scarcity of marine deposits representing the different 

 horizons in America. 



The geographic distribution of the 63 post-Paleozoic species shows 

 that 30 are found along the eastern and southern border of the United 

 States, 15 on the Pacific Coast, and 18 from the Arctic Circle south to 

 about the fortieth parallel and between the one hundredth and the one 

 hundred and twentieth meridians. 



The Trias of eastern North America, with its unfavorable shore 

 deposits, has but one species, while the Cordilleran Sea^ to the east of 

 the Rocky Mountains has 7, and these were there followed by 5 other 

 species in the Jurassic system. A larger brachiopod fauna may have 

 existed in the deeper waters of the Atlantic Trias, but nothing of it is 

 known. In Cretaceous times conditions were again more fav^orable, 

 10 forms being recorded from the Atlantic border of North America, 10 

 from the Pacific, and 6 from the interior Cordilleran Sea. Toward the 

 close of the Cretaceous the Cordilleran Sea became more and more 



iZittel, op. cit., p. 714. 



Ubid., p.716. 



^Fdrtlie area.s covered by this and the MissiRsippian .and Appalachian seaa, see Walcott's presi- 

 dentinl .address, Geologic time as indicated by the sedimentary rocks of North America; Proc. Am. 

 Assoc. Adv. Sci., Vol. XLII, 1893, 



