6 RATHBUN 
is the only one so far published, but it is necessarily incom- 
plete. 
Geographic distribution.—The following points are brought out 
in the accompanying table of distribution: 
That Arctic species often continue southward through Bering 
Strait along the west coast of Bering Sea to Okhotsk Sea and the 
Kurile Islands. 
That some of these species may also stretch along the Alaska 
shores southward, occasionally to Puget Sound or even farther 
south. 
That the winter line of floating ice in Bering Sea determines 
the northern limit of many species. This line extends approxi- 
mately from the neighborhood of Nunivak Island westward just 
north of the Pribilof and Commander Islands to the Kamchatkan 
shore. 
While many species range continuously from this line south- 
ward to California, others indicate a division of that stretch of 
coast-line into several faunz. So far as the Crustacea are con- 
cerned, the vicinity of Kadiak appears to be a boundary between 
subregions. Aleutian species, however, are often found out of 
their normal region, in the cold glacier-fed bays and sounds of 
southeastern Alaska. 
The Straits of Fuca and Puget Sound also form a partial boun- 
dary between species, partial because, while nineteen species have 
Puget Sound for a southern limit, and nine species find here their 
northern limit, seventy others run uninterruptedly north and south 
of this point. 
The vicinity of Monterey Bay, California, is a more striking 
barrier to species than those above mentioned, the crustacean 
fauna south of that promontory being strongly Mexican or Lower 
Californian in character. 
In exceptional cases, as in Philyra pisum and Cancer amphiv- 
tus, a Japanese species is found to occur in approximately the 
same latitude on the American coast, without obvious connection 
by way of Alaska. 
As is to be expected, the inhabitants of the deeper waters of 
Bering Sea (below 500 fathoms) are likely to extend much 
farther south in the North Pacific Ocean than the shoal-water 
