HYDROIDS OF BEAUFORT, NORTH CAROLINA. 34I 



GEOGRAPHICAL DISTRIBUTION. 



A lengthy discussion on geographical distribution would be out of place in connec- 

 tion with so limited a number of species, but a few general remarks may be appropriate. 

 The locality is of very great interest because it is less than loo miles from Cape Hatteras, 

 which has been considered somewhat a rival of Cape Cod as a divisional point for different 

 groups of marine forms. A study of the distribution of these few species is illuminating, 

 though what may be true of hydroids is not necessarily true of other forms and in some 

 cases might seem to be necessarily untrue of them. 



Of the 51 species described in this paper, only one, Hydractinia Carolina, is new, and 

 only four others are new to the east coast of North America, namely, Scandia mutahilis, 

 Aglaophenia acacia, Plurmdaria setaceoides, and Halccium repens, this last not being 

 diagnosed with certainty. Two more, Halecium bermudense and Halecium naniim, 

 have not been reported near the mainland, the former only by Congdon from the Ber- 

 mudas, and the latter by the same investigator and also by Billard from the Antilles. 

 Thuiaria fahricii and Filellum, expansum have not been reported south of Greenland. 

 Thirty-one species have been reported north of Beaufort, along the Atlantic coast of 

 North America, and 24 south (this does not include the Bermuda forms), while 10 species 

 have been reported both north and south. Of these 10 latter, 4 are usually considered 

 northern forms and 6 are forms usually found in tropical or subtropical waters which 

 have been carried northward largely with the sargassum in the Gulf Stream. Of the 19 

 species described by Congdon from the Bermudas, 1 1 were found at Beaufort. With 

 the exception of two that are northern or have a general range, all of these are tropical or 

 subtropical forms. Fifteen species have been reported from the west coast of North 

 America and i8 from Europe, while 12 are common to the west coast of North America 

 and to Europe. Seventeen species have been reported from the west coast of Africa, 

 only 7 of which are warm-water forms. Ten species have been reported from Australia, 

 5 of which are cosmopolitan and the other 5 warm- water forms. Six species are 

 reported by Hartlaub from the Strait of Magellan and the Chile coast, but they are all 

 cosmopolitan forms. 



From these few comparisons some generalizations may be made. In the first place, 

 when 31 species out of a total of 51 have been reported from the east coast of North 

 America farther north, there is no evidence, as far as hydroids are concerned, that Cape 

 Hatteras with its storms is any decisive barrier. When there is such a large percentage 

 of shore and shallow water forms common to the north and the south, one should readily 

 suppose that if the forms of the deeper water were studied, the similarity would be still 

 more marked. As it is, there is no more difference than would be found in the same 

 distance on almost any coast, due to the dropping out of certain forms and the appearance 

 of others in natural succession. It is true that only 10 of these 31 forms have been 

 reported still farther southward, but that is not surprising when it is taken into con- 

 sideration that, with the exception of the species described by McCrady more than half 



