1902.] AND ANCIENT GEOGRAPHY. 349 



northern parts of South America (Archiguiana) once formed, during 

 Mesozoic times, a part separated from the rest of South America, 

 which, however, continued eastward across the Atlantic Ocean 

 connecting with Africa. Fernando Noronha and St. Helena are 

 remnants of this land-bridge, which he calls by the name of Arch- 

 helenis. This connection was destroyed, according to von Ihering, 

 in the Eocene, or, at any rate, not later than in the Oligocene. 



To the numerous instances quoted by von Ihering in support of 

 his theory the distribution of the family of the Potamonidiz adds 

 another one, and the fact that two different subfamilies are found 

 in the Old and the New Worlds, and that the affinities of the Ameri- 

 can forms with those of Africa and Asia are somewhat obscure, 

 indicates that the connection of both is to be regarded as an old 

 one and that it has been severed long ago. Therefore its existence 

 in Mesozoic times and destruction in the beginning of the Terti- 

 ary, as maintained by von Ihering, has much in its favor. 



Taking up the geological side of this question, we first have the 

 broad Jurassic connection between Africa and South America 

 assumed by Neumayr (1890). According to this author, and also 

 according to Suess (1888, p. 677 ff), the whole of the southern 

 Atlantic Ocean ^did not exist neither during the Jurassic nor 

 during the older Cretaceous (Naumayr, /. c, p. 376), since no 

 traces of deposits belonging to these periods are found in West 

 Africa or on the eastern shores of South America It was not until 

 the beginning of the Upper Cretaceous that sea washed the eastern 

 parts of Brazil (/. c, p. 389). But the connection of both conti- 

 nents persisted even then, although in a limited degree, and dis- 

 appeared entirely as late as after the beginning of the Tertiary (/. c, 

 p. 397). Its last remnant (/. c. , p. 493) was formed by a chain of 

 islands which extended in the Oligocene from tropical Africa to 

 South America and the West Indies. 



This view, however, is not accepted by Koken. In his map 

 (1893, Pi* x ) tne Cretaceous continents of South America and 

 Africa are absolutely separated in the earlier as well as in the later 

 part of this period, and the Atlantic coast lines of both generally 

 agree with the present ones. In the older Tertiary Koken (pi. 2) 

 draws an island chain (Brazilo-Ethiopian islands) from the West 

 Indies to Africa. 



As far as it refers to the Cretaceous period, Koken seems to be 

 mistaken. Although formerly it was supposed that Lower Creta- 



