1895.] The First Fauna of the Earth. 885 
course, regarded with great interest, as they carried life on the 
globe further back in time than had ever before been supposed 
possible. The evidence adduced by Dr. Emmons as to their 
great age was not, however, accepted by the geological world. 
Geologists were loath to believe that so highly organized an 
animal could have existed at so 
early a period. Some believed 
the rocks containing the fossils 
were younger than the Potsdam, 
instead of being older, considering 
that even if they were really lying 
underneath the Potsdam sand- 
stone, that it was by reason of a 
fault or dislocation which had re- 
versed the original position of the 
two formations. In fact, the ex- 
istence of the possibility of a series 
of sedimentary deposits below the 
Potsdam was denied, although 
this has long since been admitted. 
Fig. 3. Ptychoparia (Atops); trili- Yet long and bitter has been the 
neata. The first trilobite known from controversy Over this Taconic sys- 
the Cambrian rocks. tem ; and while it is now known 
that Emmons included rocks of various ages in his new terrane, 
no one disputes the fact that he was the first to record evidence 
of the existence of animal forms in what are, at present, re- 
garded as the oldest fossil-bearing rocks of the globe. 
Previous to Emmons’s work in North America, Sed gwick and 
Murchison had been studying the formations of England and 
Wales; and in 1835, Sedgwick proposed the name “ Cam- 
brian” for a series of rocks in Wales, supposed by him to be 
without life. A little later, about 1837, Murchison proposed 
the name “Silurian” for another and a higher series, which 
he thought contained the earliest forms of animal life. A con- 
flict soon arose between the adherents of the two systems. 
Murchison extended his Silurian downward as fossils were 
found at lower and lower horizons, against the vigorous oppo- 
sition of Sedgwick. It was not until the characters of the 
