344 C. SCIIUCIIEKT MARINE INVEKTEBKATE EOSSIL FAUNAS 



among the trilobites, the evolution among the Dalmanites (in Ilausman- 

 nia, Corycephalus, Proholium, and Odontocheile), the lichadids {Dicra- 

 nurus), and the phacopids. Since these faunas are known on either side 

 of the Atlantic Ocean, or, better, Poseidon, we speak of them as of the 

 Atlantic realm. There is also a Pacific realm of this time, but as yet its. 

 faunal elements are known only in Nevada. 



Austral Devonian realm. — To understand correctly the very interesting 

 higher Lower Devonian faunas, we will begin our studies in the high 

 x4.ndes of Bolivia. Here d^Orbigny for the first time in 1842 described a 

 few fossils, correctly referring them to the Devonian, and further addi- 

 tions were made by Morris and Sharpe in 1846, and by Salter in 1861, 

 Finally the greatest additions to these faunas were made by Steinmann 

 and his students A. Ulrich (1892) and Knod (1908). Now we know a 

 fauna of more than 100 forms that occurs through a thickness of about 

 2,300 feet of gray or yellow micaceous well bedded sandstones and dark 

 shales. Its age is of the higher Lower Devonian, comparable with the 

 Oriskanian of the United States and the Taunusian and Coblenzian of 

 Germany. 



Another center of geologic endeavor in South America was started in 

 1874 by Professor Hartt, of Cornell University, in his explorations of the 

 iVmazon Valley. His field-work on the Devonian of Brazil was further 

 extended by 0. A. Derby between 1878 and 1890, and the faunas have 

 been described by Eathbun (1874, 1878), Katzer (1896 to 1903), and, 

 above all, by J. M. Clarke (1890 to 1913). The Lower Devonian faunas 

 of Brazil amount to about 75 species; for the whole of South America, 

 however, including the Falkland Islands, the total is about 240 forms, 

 and most of its elements have been modernized by Clarke. 



The higher Lower Devonian faunas are noAv known from the Andean 

 region of Bolivia, Peru, and Argentina : from the Amazon Valley along 

 the rivers of Maecuru, Curua, and Erere; from the Brazilian States of 

 Parana and Matto Grosso, and from the Falkland Islands. A very sim- 

 ilar fauna is also known in the Bokkeveld formation of southeast Africa 

 and in the Sahara desert at Tasile. It represents the Leptoccelm flahel- 

 lifes realm of the higher Lower Devonian, the austral seas that overlapped 

 on the old land Gondwana. These austral assemblages are characterized 

 by the almost total absence of corals, echinoderms, bryozoans, and cepha- 

 lopods, with a marked development of gastropods of the Bellerophon and 

 capulid types, an abundance of Connlnria, and. alcove all, a great variety 

 of peculiar brachiopocls. The characteristic genera of the last-named 

 class are Hipparionyx, very large flat Clwneies, Eatonia, Tropidolepiiis 



