1918] Essenbcrg: Distribution of the Polynoidae 175 



been obtained at different places along the coast from Cape Mendo- 

 cino on the north to Los Angeles on the south. 



Of the forty-nine species of Polynoidae restricted to the waters of 

 the Pacific coast of North America two species, Halosydna insignis 

 and Lepidonotus cacloris, have the widest range of distribution of all 

 the polynoids known on this coast. The distribution of the former is 

 recorded from Alaska and Puget Sound to Point Conception. So far 

 as is known, however, this species has not been obtained either in the 

 Arctic Ocean or in tropical regions south of Cape San Lucas. Lepi- 

 donotus caeloris occurs in great abundance along the coast of Cali- 

 fornia, from Monterey to Cape Colnett. It is also recorded from the 

 coasts of Japan and from the waters of Alaska. The remaining forty- 

 seven non-cosmopolitan species of Polynoidae of this coast may be sub- 

 divided into definite groups on the basis of their geographical dis- 

 tribution. Each group belongs to a particular life zone. 



The generally recognized life zones on the Pacific coast are : ( 1 ) 

 the tropical zone, extending from the equator to Cape San Lucas; (2) 

 the north subtropical zone, extending from Cape San Lucas to Point 

 Conception; (3) the north temperate zone, extending from Point 

 Conception to Cape Flattery; (4) the lower boreal zone, from Cape 

 Flattery to the Bering Sea; and (5) the upper boreal zone, from the 

 Bering Sea northward (Setchell, 1915). 



Each zone includes a distinct group of Polynoidae. Since there 

 are but very few strictly upper boreal or tropical species of Poly- 

 noidae represented in the annelid collection of the L^niversity of Cali- 

 fornia, these two zones are of less importance in connection Avith this 

 work and do not enter into the discussion on the following pages. 



The following table (1) shows the geographical distribution of 

 the Polynoidae. Certain species may be grouped as strictly subboreal, 

 others as temperate, and still others as subtropical, although there are 

 a few exceptions. Occasionally a species may be found in two adjacent 

 zones, and again species may be found occupying very limited areas, 

 not even extending throughout one entire zone included between the 

 points given. It should be remembered that the distribution of some 

 of the species is as yet inadequately known. 



