212 University of California Publications i)i Zoology [Vol. is 



is found some distance away from the shores, while in other places 

 the bottom nearer shore is muddy and soft (Willemoes-Suhm, 1874). 

 The best feeding grounds of the oceanic fauna are undoubtedly the 

 shore regions or littoral zone, where plant and animal life occurs in 

 great abundance. Hence the Polynoidae and annelids in general are 

 more abundant in the littoral zone. With an increase in distance 

 from the shore and with an increase in the depth there is a decrease 

 in individual numbers of the Polynoidae but a proportionate increase 

 in genera and species. On this coast, although the littoral Polynoidae 

 are very abundant so far as individual numbers are concerned, yet 

 there are only four genera and fifteen species (table 4). Of these 

 four genera, one, Eiinoe, is not common in subtropical littoral zones but 

 occurs as a littoral form in the boreal and subboreal regions, and as 

 an abyssal form in the temperate and subtropical zones. This leaves 

 only two strictly littoral genera in the subtropical and temperate zones. 

 Of the exclusively deeper water polynoids we have seven genera and 

 fourteen species. The number of deep water genera is about two 

 times that of the littoral polynoids, and the number of species about 

 equal. The number of individuals, however, is very small, and some 

 deep water genera are known from but a single representative. 

 Although we have to admit that the deep water survey is less com- 

 plete than that along the shore, nevertheless the data show that there 

 is an increase in genera with an increase in depth, and that the great- 

 est uniformity prevails among the littoral polynoids. The species 

 most abundantly represented on this coast, such as Halosydna insignis, 

 H. calif ornica, H. carinata and H. intcrrupta, are very much alike in 

 their general appearance so that by superficial observation they are 

 more likely to be taken as individuals of the same species. The same 

 similarity may be observed among other species and genera and great 

 diversity of species and genera found among the deep water species 

 is not as common among the littoral species. Food conditions near 

 the shore aid to increase and multiply the littoral polynoids. On the 

 other hand, the scanty food supply in the depths, other things being 

 equal, will naturally check the increase of the deep water polynoids. 

 The deep water species of Polynoidae evidently do not inhabit the 

 depths from choice, but many of them have been carried from the 

 colder boreal regions and have found there identical temperature con- 

 ditions although the food conditions are greatly different. Other 

 polynoids have been driven off shore by waves or storms. Secondly, 

 since the food supply in the great depths is insufficient only com- 



