14 SYNOPSIS OF AMERICAN FOSSIL BRACHIOPODA. [bull. 87. 



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

 nuity when compared with the Alpine Trias, from wliicli Bittner 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 system 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 iu the Carboniferous or Permian. The 

 superfamilies Acrotretacea, Obolacea, and Pentameracea have died 

 out, while the Lingulacea, Disciuacea, 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 Rhynchonellid;e.' The Cretaceous has 26 species, 

 also a meagerrepresentation, and yet " outside of Europe, North America 

 is the most imi)ortant for the occurrence of Cretaceous Brachiopoda.'" 

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

 between the European and American Oenozoic brachiopod faunas is 

 l^artly dne to the scarcity of marine deposits representing the ditferent 

 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, Avith 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 iu 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 favorable, 

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

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

 close of the Cretaceous the Cordilleran Sea became more and more 



'Zittel, op. cit., p. 714. 



»Ibkl., p.716. 



'Fortho arfias covered by this and (lio Mississiiipiiiii .ind A]>pala(liiaii soas, n(-o Walcott's prosi- 

 (leiitial address, Geologic time as indicated l)y tlie seiliiueutary rocks of Nortli Anu-riea: Proc. Am. 

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



