1921] Schmitt: The Marine Decapod Crustacea of California 289 
San Diego, and these two were both common to the other two localities. 
At San Diego, however, the opportunities for collecting were compara- 
tively limited, and but a short time was spent at that place.’’ 
That neither Fraser, Torrey, nor Coe considered the region south 
of San Diego, and that thirty-three of the California decapods at 
present find the southern limit of their range at San Diego is no doubt 
due to the extreme dearth of material from the west coast of Lower 
California. Except for the explorations of the elder Anthony 
(A. W.) and a number of scattered stations of the ‘‘ Albatross’’ the 
littoral portion of this region remains today almost as much a “‘terra 
incognita’’ as it was before the expeditions of the California Academy 
of Sciences to Magdalena Bay and the ‘‘Cape.’’ It still offers an 
extremely fertile field for the ambitious collector. 
But Dr. A. E. Ortmann (1896a) was the first to point out the 
continuity of the faunal region under discussion, with whose ‘‘ Pacific 
Boreal (Littoral) Subregion,’’ lying south of the Aleutian Islands 
it closely corresponds. 
Unlike almost all other students of zoogeography who seem to have 
followed the inductive method and constructed their zoogeographical 
divisions according to the actual distribution of animals, Dr. Ortmann 
followed the deductive method and constructed his divisions according 
to the differences in the physical conditions influencing the distri- 
bution of animals. Of these ‘‘probably no single factor is a more 
effective barrier to the extensive geographical range of marine animals 
than is that of temperature’’ (Mayer, 1914, p. 3), for, to use the 
words of Doflein (1904, p. 269), ‘‘Alle Erfahrungen der letzten Zeit 
haben uns mehr und mehr gelehrt, dass die Verbreitung der Meeres- 
tiere am meisten von den Wassertemperaturen beeinflusst wird.’’ 
Torrey, Coe, and Verrill all realized the importance of the in- 
fluence of temperature on the distribution of the forms upon which 
their studies were based. 
Though Dr. Torrey spoke of his faunal differences as being cor- 
related with certain geographical differences, he said (1902, p. 7): 
North of the [Alaska] peninsula is a region whose waters are largely covered 
with ice for more than half of each year. South of the peninsula begins a vast 
stretch of coast which is washed by the comparatively warm waters of the Japan 
Current. This current is probably accountable for the absence of abrupt transi- 
tions between the faunal area which I have tried to schematize above [quoted 
on p. 287 of this paper], and the exceedingly long distances to which some of the 
northern species have been distributed southward. The temperature of the current 
varies gradually with latitude, however, and that offers some explanation for the 
small faunal differences that exist. 
