SLODIES FO SRODENLS: 487 
tion of a species all over the earth has led to the theory that 
species, like individuals, have a limited life, and that in time they 
- reach a stage of development where they can go no further, and 
then of necessity die out. 
This idea would be all very well if species dropped out one at 
a time, but in reality they usually go and come by faunas. It 
would seem, then, that changes in physical geography have had 
more to do with the extinction of faunas then anything else. 
This becomes the more probable when we reflect that species are 
not extinguished contemporaneously over the earth, but rather 
that their appearance and extinction have been used by geologists 
in a misleading way to prove synchronism of strata. 
Remarkable cases of survival of types have long been known, 
as of Zrigonia in the Australian waters, and of Pholadomya in the 
mntlless Sinvivials. of staunas ware constantly coming to light. 
Dr. W. H. Dall* has shown that a large proportion of the Pliocene 
and even Miocene invertebrates of the Southern Atlantic Gulf 
states are still found living in the archibenthal region off the 
present coast. The same thing is true of the California coast, 
but here we have an even more remarkable example. Dr. A. C. 
Lawson,’ from purely geologic evidence, has reached the con- 
clusion that Santa Catalina Island has remained above water 
during Quaternary time, while most of the neighboring country 
was submerged. This stability of conditions has shown itself in 
a unique survival of the marine fauna, for Dr. Cooper’s3 list of 
the fossil mollusca of the California coast shows five species still 
living on Catalina that are known elsewhere only as fossils, and 
many species that are now known living in other remote zodlogi- 
cal provinces. Similar cases of survival occur in ancient geo- 
logic formations. 
Dig Com ene Nev scaled matte ntionmtoma reappearance of a 
Waverly fauna in the Burlington of Missouri. A similar occur- 
* Bull. Mus. Comp. Zool., Vol. XII., No. 6, p. 186. 
? Univ. Calif. Bull. Dept. Geel., Vol. I., No. 4, p. 135. 
3 Calif. State Mining Bureau, Seventh An. Rep. 1887. 
4 Am. Jour. Sci., Dec. 1892, p. 447. 
