6 RATHBUN 



is the only one so far published, but it is necessarily incom- 

 plete. 



Geographic distribtitioti. — 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 faunae. 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 amphioe- 

 tiis, 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 



