668 REVIEWS 
close of the Cretaceous, with its accompanying disfiguration of topog- 
raphy, ‘‘was continuous to the present, or alternated with long periods 
of quiescence, cannot be answered.” Thus volcanic activity accom- 
panied the orogenic movements of Miocene time, giving “the most 
cataclysmic revolution of all geologic time and place.” 
Summarizing the evidence touching the union of the northern and 
southern continents, it is said that nothing is known of their relations 
in the Paleozoic; that land may have been continuous between them 
in the early Mesozoic; that it was probably so in the Cretaceous ; and 
that in the Tertiary period only, in later geologic time, does the con- 
nection of the oceans across tropical America seem to have been pos- 
sible, For their connection, even in this period, the evidence is 
much less conclusive than is commonly believed. For such connec- 
tion “no stratigraphic proof has been discovered,” and the physical 
character of the Tertiary sediments seems to be distinctly against any 
broad union. The only evidence pointing to their connections is 
paleontological, and even this is meager. In a single terrane of the 
Eocene, five species of mollusks on the Caribbean side of the Isthmus 
occur also in the Tejon Eocene of California. These species are held 
to indicate that in the Tejon epoch there was at least a shallow com- 
munication between the oceans, and that ‘to this epoch alone can the 
date of an interoceanic connection be assigned by direct palezeontolog- 
ical evidence. . . . . All the authentic biologic and geologic evidences 
are entirely opposed to the possibility of a communication between 
the two oceans across the Isthmus or tropical American region in 
Pliocene or Pleistocene time.” The statement of Upham, Spencer, 
and others, that marine Pleistocene fossils have been found at great 
heights on the Isthmus, is said to be erroneous. 
Io De) Se 
