26 AMERICAN HYDROIDS. 



These regions are defined under tlie discussion of the distribution of the Sertularidre on 

 page 47 of part 2 of this work. The regions adopted for the Campanularidas are practically 

 the same as for the Sertularidse, with the following exceptions: 



The Californian region is extended to include the Pacific Coasts of tropical South 

 America. 



The Scandinavian region is extended to include the Arctic regions immediately north 

 of Europe. 



An "Indo-Pacific" and an "African" region are added. 



The North Atlantic coast of the Unitetl States appears from this showing to be richer in 

 cami)anularian life than any other region, there being 30 species out of the 81 included in the 

 American hydroid fauna, or 37 per cent. It is altogether probable, however, that if an equal 

 amount of collecting had been done on the North Pacific coast there would be found to be as 

 many or more species of hydroids from that region, including the Californian and Alaskan, as 

 are known from the Atlantic coast. 



The Californian region is extended southward to include the Pacific shores of tropical 

 America, but this extension does not result in the addition of any hydroid species. Twenty- 

 eight species have been found in this region, or about 34 per cent of the total American species. 

 This showing is due to the extension of the known range of many Alaskan species southward, 

 rather than the discovery of additional species on the Californian coasts. 



Next in importance, so far as North American waters are concerned, comes the Alaskan 

 region with 18 species, the Arctic with 12 species, and the West Indian and Canadian with 10 

 species each. 



In South American waters the Patagonian and Antarctic region leads with 21 species, or 

 about 27 per cent of the total of American Campanularidse, while the South Pacific region, 

 including Chile, has yielded but 8 species, or 10 jjer cent of the total. It must be remembered, 

 however, that South American waters have been relatively but little explored and that the 

 ultimate showing may be quite different. 



In European waters the British region leads with 21 species, or 27 per cent of the entire 

 number of known American C amp anul arid se. It is of interest to note in this connection that 

 9 species, or 41 per cent, of the Californian forms are familiar British species. This seems to be 

 further evidence of the meridianal distribution of the Hydroida from Polar regions to which 

 the present writer has called attention in previous communications.' 



The Patagonian (including the Antarctic) region proves to be almost as prolific in campanu- 

 larian forms as the British region, yielding 21 species, or 27 per cent, of the entu"e list of American 

 Campanularidse, showmg that this family has about twice as many representatives in the 

 Patagonian region as has the Sertularidse. 



Two genera have their center of distribution in this region, i. e., the genera Orthopyxis and 

 Silicularia, with an aggregate of 11 species. Of the remaining 10 species found in this region 

 5, Campanularia Integra, C. verticillata, Ohelaria gelatinosa, Obelia geniculata and 0. longissima, 

 are species of very wide distribution belonging to genera which are almost cosmopolitan. 



The West Indian region is the home of 10 species, or 12 per cent, showing that the cam- 

 panularians have a relatively ])oor proportion of species in our southern waters. 



The Brazihan and vVfrican regions are apparently the poorest of all in representatives of 

 this group. While this is doubtless largely due to lack of extensive exploration in these regions, 

 it is nevertheless jjrobably a fact that they are poor in campanularian life. We must, moi-eover, 

 bear in mind the fact that this table includes only those Campanularidse that are known to 

 occur in American waters, and that a similar table prepared to illustrate the distribution of 

 European forms would probably include a larger number of forms from the African region. 



The remarkably wide distribution of individual species of hydroids 'is indicated in this 

 table which shows no less than 30 species that are common to Europe and America. That is, 

 nearly 38 per cent of American Campanularidse are found also on the other iside of the Atlantic. 



' Papers from the Harriman Alaska Expedition, vol. 21, the Hydroids, 1901, p. 162. American Hydroids. pt. 2, 

 1904, p. 48. 



