l8o NUTTING [162] 



broken faunal area that might properly be designated as Alaskan. 

 From the number of arctic species included in this area it is not 

 improbable that it extends northward along the shores of Bering 

 Sea. 



Dr. Clark agrees with Dr. Dall that there is a distinct faunal 

 difference between the region east of the Shumagin Islands and 

 that west of them. The material added since the publication of 

 his paper, however, seems to prove that this difference is only 

 apparent and due solely to lack of exploration. 



The most important thing to be noted in that part of the table 

 devoted to general distribution is the Holarctic distribution of a 

 number of species. Of the eighteen species known to occur in 

 the Arctic region, no less than fifteen also occur on the European 

 coast, fourteen on the Atlantic coast of the United States, and 

 thirteen on the Pacific coast as far south as Puget Sound. An 

 examination of the table shows further, that the Hydroid fauna 

 of Alaska, as represented by the Harriman collection, includes 

 fifty-three species in all, of which eighteen are Arctic in fact, 

 having been secured in Arctic waters ; four others are in all 

 probability Arctic, being found both in European and American 

 waters ; four are, so far as is known, confined to the Alaskan 

 and Pacific coast south to Puget Sound ; twenty-five are thus far 

 known from Alaska only, and two are Californian. If we rec- 

 ognize the Alaskan faunal region as extending to Puget Sound, 

 and include those species actually known to be Arctic, together 

 with those in all probability Arctic, in a group which may justly be 

 called Arctic, the following significant analysis of the faunal rela- 

 tions of the collection may be made ; Alaskan species, twenty- 

 nine ; Arctic species, twenty-two ; Californian species, two. This 

 shows that fifty-five percent of the hydroid fauna as a whole is 

 peculiar to Alaska, but that there has been a strong invasion from 

 the Arctic regions of the Holarctic species constituting about 

 forty-one percent of the collection, and that only two species, 

 or less than four percent, are Californian. If all the species 

 known to occur in Alaska were included in the computation the 

 result would be a larger percentage of Alaskan species, a cor- 

 responding decrease of the Arctic species, and the addition of 

 one or two Californian species. 



