230 F. BR. Cowper Reed— Fauna of the Bokkeveld Beds. 
were published prior to the Saharan discoveries. Schwarz (33) has 
called Katzer’s ‘ Atlantic-Ethiopian Continent’ by the simpler name 
of ‘ Flabellite Land,’ after the characteristic fossil Leptocelia flabellites. 
Frech (26, p. 239) has proceeded on the view that the Bokkeveld 
beds are of Lower Devonian age, and his restoration of the ancient 
geography differs somewhat from Katzer’s. By the insertion of 
a narrow strait cutting across Katzer’s ‘ Atlantic-Ethiopian Continent’ 
and separating his own ‘ Indo-African Continent’ from his ‘ North 
Atlantic Peninsula’ (which corresponds more or less with the northern 
half of Katzer’s aforesaid continent) he brings into connection the 
West European and South African faunas, which Katzer failed to do. 
The latter’s ‘Indian Connecting Sea’ to the east of the present 
African continent finds no place in Frech’s map, and we notice, too, 
the practical absence of the great ‘Southern Continent’ in the South 
Pacifie, and the consequent merging of the ‘ Brazilian Connecting Sea’ 
into the main Pacific Ocean. The ‘Northern Helderberg Sea’ of 
Frech’s map corresponds somewhat to Katzer’s ‘ Appalachian Bay’ 
and passes southwards into the ‘Southern Helderberg Sea,’ which is 
represented as covering most of South America. A ‘South Atlantic 
Island’ more or less prevents a direct communication between the 
Cape and the Falkland Islands. 
The restoration of past geographical conditions is not as a rule 
satisfactory, and such maps must be largely speculative, the real 
causes which determined the differentiation of the faunas being rarely 
ascertainable. The habit of imagining the existence of land barriers 
to account for differences in contemporaneous geological marine 
faunas may be carried too far, particularly in dealing with the 
distribution of molluscan faunas indicating water of moderate depths. 
The factors which are responsible are much more subtle and 
intangible. The present arrangement of marine zoological provinces 
round the coasts of the Atlantic affords a lesson and a warning. 
Apart from lithological characters of the beds and other geological 
considerations, the mere faunistic difference of contemporaneous beds 
is quite compatible with their deposition in the same ocean basin either 
along continuous coastlines or on opposite shores with open sea between 
them and without any land barriers to separate them. Differences of 
climate are frequently invoked to explain such difficulties, but we 
now know from marine biological research that climate is only one 
factor, and not by any means the most important one, in determining 
the characters and distribution of marine littoral faunas. Walther (30) 
has especially laid stress on the importance of bearing this in mind 
in dealing with the fossil contents of marine formations, and the 
modifications of Neuwmayr’s Jurassic theories which recent work in 
South America, the Arctic regions, and elsewhere has necessitated, 
emphasise the wisdom of allowing for the action of other factors. 
ConcLUsIONs. 
Summing up the results of the foregoing survey we are led to the 
following conclusions :— 
1. The Bokkeveld fauna is more closely allied to that of the 
Devonian of South America than to that of any other area. 
2. This southern Devonian fauna is marked by the special develop- 
ment of certain peculiar subgenera (Anchiopella and Metacrypheus), 
