542 DR. S. J. HICKSON ON 



subregions, one north and the other south of the British- 

 American frontier. 



There is, of course, no zoo-geographical barrier between these 

 two subregions, and we should expect to find considerable over- 

 lapping, some of the characteristic southern genera appearing 

 in the northern subregion and vice versa. 



One of the characteristic features of the northern subregion is 

 the occurrence of genera and even species that are familiar to us 

 on our North Atlantic coasts, suggesting that they are the 

 representatives of a circumpolar fauna. Thus Professor Herdman 

 (1898, p. 249), wi-iting about some simple Ascidians collected in 

 Puget Sound, says, " I think it may with truth be said that 

 all the Ascidians I collected in this arm of the N. Pacific are 

 closely related to familiar species on our own North Atlantic 

 coasts. This, taken with the similarity between the two faunas 

 shown in other groups, suggests the possibility that there is a 

 common northern circumpolar mai'ine fauna which extends south- 

 wards on the western coasts of Europe and America." This 

 view is supported by Walker (1898, p. 269), who says, in writing 

 on the Crustacea collected by Herdman in the same locality, 

 " Besides the species in the collection that are absolutely identical 

 with the British species, the resemblance between others is 

 remarkable." 



In an account of the Hydroids of the Alaskan expedition 

 (1910, p. 179), Nutting gives reasons for believing that Puget 

 Sound is a natural region of demarcation between faunse, but 

 Eraser (1911), in his account of the Hydroids of the Vancouver 

 Island region, considers that there is no justification for a state- 

 ment that there is a distinct break at any point along the coast. 

 " At the present time," he says (p. 7), " out of a total of 

 196 species there is a record of 155 species from the Vancouver 

 Island region and north of it, and 88 south of that region. No 

 less than 47, or 24 per cent, of the whole number, are common 

 to the two. Furthermore, 22 species that are found north of 

 Vancouver Island are found in the Vancouver Island region as 

 well as in the region south of it." 



As regards the Alcyonarian fauna of the Oregonian region, we 

 possess some knowledge of the genera and species found on the 

 coast of California, i. e. the southern subregion, thanks to the 

 researches of Nutting and others, recently summarised and 

 i-evised by Klikenthal (1913), and it is therefore of no little 

 interest to compare them with the few species collected off 

 Vancouver Island and in the Gulf of Alaska that are described 

 in this paper. 



The following is a list of species of Alcyonaria now known to 

 occur in the region of Puget Sound and north of it : — 



Clavulana tnoreshii. Caligorgia fraseri. 



Paragorgia arhorea. Psammogorgia teres (sp. ?). 



Primnoa willeyi. Osteocella sejjtentrionalis. 



