212 Fortieth Annual Meeting 



ject to frequent temporary and sudden changes because of 

 the influence of land conditions and the shallowness of the 

 waters affected. 



The character of the littoral sea-floor differs widely from 

 that of the deep seas. More than half the entire oceanic 

 bed is covered, often to a great depth, with a continuous 

 layer of radiolarian and globigerina ooze, composed of mil- 

 lions of skeletons of protozoan plankton, which have grad- 

 ually been deposited during the geologic ages, while the 

 deepest portions are covered with a layer of red clay. 

 Hence the deep sea bottom presents comparatively uniform 

 conditions. 



But in the shallow waters near the shore diversity in- 

 stead of monotony is the keynote. In one place swift tidal 

 currents have scoured the bottom, laying bare the rocks. 

 In another a river is depositing its cargo of silt, which 

 when opposed by tidal action forms bars of mud and sand. 

 Elsewhere, the winds and waves have eaten away the ter- 

 restrial soil from promontories, leaving a boulder-strewn 

 sea margin, while the tidal currents carry the loosened soil 

 into sheltered harbors where it is dropped to form mud 

 flats. On coasts like those of Maine, cliff's rise out of the 

 sea, their walls full of crevices, pockets, and caverns, which 

 become more hollowed out by the waves. The constant 

 grinding of rock fragments, too, reduces granite and quartz 

 to fine sand which, deposited over the sea bottom, is here 

 and there washed up by the waves to girdle exposed reaches 

 of shore. Such is the setting for the littoral fauna that 

 fringes our coast. Let us briefly consider some of its gen- 

 eral features. 



The diversity of the inanimate coastal conditions is re- 

 flected in the fauna, and is expressed largely in specializa- 

 tions to the respective environments. Each typical locality 

 becomes, as it were, a center. 



As in the oceanic association, the shore fauna may be 

 classified into plankton, nekton, and benthos. The plank- 

 ton of our northern coast differs from that of the deep sea 

 in that there are relatively few of the larger floating ani- 



