6 University of California Publications. [zoologt. 



according to which 69 species (49 'V) occur north of Sitka, 

 9G (68.5%) north of Paget Sound. 



The only geographical barrier of any magnitude is Alaska 

 Peninsula. The fauna of Alaska north of the peninsula is dis- 

 tinguished from that south of it by the absence of any represen- 

 tatives of the Haleciidae, Lafmidae and all the families of the 

 Gymnoblaxlfa except three species of Pmnariidae, which are 

 restricted to that region; also by the small number of species (2) 

 of Campanulariidae, in representatives of which family the 

 fauna of Alaska south of the peninsula is so rich. The fauna 

 of the Aleutian Islands belongs essentially to that of Alaska 

 south of the peninsula. Of the nine species distributed between 

 Kyska Island and Akutan Pass, none occurs north of the islands, 

 although five occur in the Southern Alaska region. 



From Alaska Peninsula to San Diego there are no abrupt 

 transitions in the fauna. It is possible, however, for purposes 

 of comparison, to divide this great region into four sub-regions. 

 The first extends from Alaska Peninsula south to Sitka. It 

 possesses a large number of species (59, IS of which are peculiar 

 to it) belonging mainly to the Campanulariidat and Sertulariidat : 

 there are relatively large numbers of Haleciidae (7) and Lafmidat 

 (6). The second sub-region includes the fauna of Puget Sound, 

 Vancouver Island and vicinity. There are 50 species, of which 

 lit are peculiar to the region; 2i' are Campanulariidae, of 

 which 10 are found in the first sub-region: 14 are Sertu- 

 lariidae, 9 of which are found in the first sub-region; ."> are 

 Huh riuliii , of which but one is found in Alaska and one south of 

 Puget Sound. The two species of Lafmidae are Alaskan; the 

 four species of Plumulariidae includes the single Alaskan species. 

 Both first and second sub-regions contain families of Gymnob- 

 lastea, though no species are common to the two. The third sub- 

 region comprises San Francisco Bay and vicinity, including 

 Monterey Bay. There are here no representatives of the Lafmidae 

 and Haleciidae. Six species are peculiar to it, all of which are 

 Gymnoblastea, including a Clara and a new Hydractinia. The 

 fourth sub-region comprises Southern California, south of Point 

 Conception. The fauna contains a relatively large number of Plu- 

 muluriidae (12, of which 8 are local) and Sertulariidat (14. of 



