8G GENESIS OF THE ARIETID^. 



The principles of geographic distribution first announced by Marcou 1 have 

 been carried further by Neumayr, 2 who has defined the homozoic bands of life 

 in the faunas of what he has denominated the Mediterranean, Central European, 

 and Russian provinces. 



Neumayr, in his article " Ueber climatische Zonen der Jura und Kreide- 

 zeit," 3 describes the boundary between the Mediterranean and the Central Euro- 

 pean provinces. This line, as far as traced by him, begins at the east between 

 the Donetz and the Crimea, at about 47° north latitude, and runs thence to the 

 easterly end of the Carpathians; thence, north-northwest to the neighborhood of 

 Krakau ; thence, southwest towards Vienna, and south of Briinn ; thence, west- 

 erly to the neighborhood of Lake Constance ; thence, west-southwest, and later 

 southwest through southeastern France; thence, across the Gulf of Lyons to 

 Spain, and across that country and Portugal to between 38° and 39° north lati- 

 tude on the Atlantic. This author regards the Mediterranean province south 

 of this line, and the Central European province north of it, as respectively parts 

 of two homozoic bands, which encircled the earth during the Jurassic period. 



The Central European province was defined by Neumayr, in a general way, 

 as including the British Islands, France, German}', Bohemia, Moravia, and Poland, 

 north of the line described above, and perhaps the Dobrudscha region. The 

 Jura north of these countries was included in his Russian province,' which con- 

 tained Central Russia, Petschora Land, Spitzbergen, Greenland, and perhaps 

 Vancouver's Island in North America. Neumayr quotes the works of various 

 authors upon the fossils found in South America, and concludes that the Jura in 

 Bolivia, Chili, the Argentine Republic, Columbia, and in Central Amex-ica is 

 probably Mediterranean. He thinks also that the few fossils found in the United 

 states indicate the presence of a Central European fauna. 



Waagen, in his " Fauna of Kutch," shows that India is a distinct basin, con- 

 taining forms of the Upper Jura found in the provinces of the Mediterranean 

 and Central Europe, besides numerous peculiar species. Steinmann is of the 

 same opinion with regard to the fauna of the Upper Jura which is found near 

 Caracoles in Bolivia. 



We have examined a number of the latter collected by Alexander Agassiz 

 at this locality, also several species collected by him at the pass of Tilibichi in 

 Peru, as well as those mentioned in the chapter " Descriptions of Genera and 

 Species " of this work, and have read Gottsche's " Paleontology of the Argentine 

 Republic." These and other sources of information show, we think, the same 

 history as in India ; namely, that this region may be advantageously separated 

 as the South American province on account of the number of peculiar species it 

 contains. There are, over and above these, also a number of forms identical with 

 those of Central Europe and the Mediterranean. We have also seen the fossils 

 of the Upper Jura, found in California, through the kindness of Prof. Joseph 



' Koches des Jura, pp. 74-01 . 230, < / seq. 



2 Ueber Juraprov. Verh. k. k. geol. Reichsans., 1871, p. 54; Ueber unverm. auftret. Cephal., Jabrb. 

 geol. Reichsans., XXVIII., 1878; and Jnrastud., Ibid., II., 1871, p. 524, 



a Denksoh Akad Wien, 1883, XI. VII.. and also Geog, Verbreit, d. Jurafor., Ibid., L., 1885. 



